Jon,

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One of the wonderful things about this program is its flexibility to accomplish so many user goals. ?As a result, the defining of the goals is a prerequisite to rendering much help when it comes to specifics. ?In your case, I would have a few questions to seek clarification about details of any needed setup. ?However, given the ideas you expressed above, I spent a couple hours creating a testing platform for them.

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? ?I started by creating a Location named "Pigeon Hole", in which I then added 5 tracks (one for each pigeonhole, capable of holding 5-6 cars plus locos and caboose). ?This location is set up as "Staging" as defined by JMRI Ops and this allows for each train in the pigeonhole to take all the cars to the fiddle area at once, leaving nothing in the pigeonhole when built. ?Each track is prevented from receiving or shipping default E or L. ?The <Custom Load Options> for this staging location, that I checked were, "Empty cars with custom loads" and "Generate loads for multiple trains" (boxes 1 & 3).
? ?I then fashioned a second Location, again defined as "Staging", calling it "Fiddleton", comprised of 4 tracks, each named "Fiddle track" and with the dash+number (e.g. -1, -2, -3, -4). ?This allows the paperwork for the Turns to just read "pick up or set out to Fiddle track". ?This means you can land the train on whichever open track you actually have available at the time. ?I selected the Staging Options, "Make track available after train is built" and "Prompt for Arrival/Departure Track into/from Staging" from the Tools-->Options menu. ? This is so the you can choose from which pigeonhole to pull a train, and onto which track in the fiddle area it should go, as well as allowing the Turn to return to the same track in Fiddleton (if so desired).
? ?The third and final Location (at least for my testbed), was labelled "15 Spur Creek" to give it a real-town-sounding name. ?The tracks here are Spurs and there are 15 of them (each with lengths of 200'), and each handling only Boxcars for my testing, but obviously can be made to handle whatever car-types you need. ?I created two schedules, one for <Merchandise> inbound and one for <MTY> inbound. ?The schedules cycle these customs upon arrival and the cars are then ready to go back out on the next Turn. ?The target destination of each schedule is back to Pigeon Hole and this prevents the cars from making "local moves". ?This was to test the viability of the original setup, but could also be tweaked to meet your needs. ?For ease of testing, I used only the two schedules, assigning the inbound <Merch> to the odd-numbered spurs, and the inbound <MTY> to the even-numbered spurs. ?Since these are the only schedules to which custom loads can be matched by the program, the only loads leaving Pigeon Hole would be <Merchandise"> or? <MTY>, but as mentioned above,? I disallowed either default to enter/leave, as a backup to hopefully prevent program hiccups.

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The reason I used "Staging" for this scenario, that answers one of your questions... JMRI "Staging" can convert the custom loads to their opposite states, and is how your cars can become ready to go back out with different custom loads.

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An important note concerning the overall (global) Option settings, is that the use of a second midpoint staging location requires selecting the "Enable car routing through Staging" option in the Tools-->Options window. ?This prevents the cars from having their loads change as they pass through Fiddleton. ?But forces the Turn train, when built, to take all the cars to "15 Spur Creek" or it will fail to build. ?This becomes a flag marker for evaluating your setup of the towns to which the Turn might eventually visit, since the car movements would have to match schedules everywhere or else the train stays put.
The load options on each of the "Fiddleton" tracks should be all left unselected, thus allowing the loads to pass through unchanged in either direction.

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I then needed to make some Routes for all this to work, so I came up with 3 and this was all the program required to get full-cycle car movements.

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Now, there has to be a train from Pigeon Hole to Fiddleton so the cars and locos can be placed onto the makeup track in the fiddle area. ?It uses Route 1 and I call it the "Pig-Fid", which is the train I build any time I want to gather cars from their pigeonhole and make up a Turn ready to go to "15 Spur Creek". ?And I get to choose which pigeonhole I want to use for this train and get to choose which track in Fiddleton to use for its arrival.
Once this train is terminated in Fiddleton, I then can either run it again and gather more cars from a different pigeonhole, placing them on a different track in Fiddleton...

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OR...

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I can build a Turn to take the first cars chosen to "15 Spur Creek". ?Having a separate train moving cars from Pigeon to Fiddleton, allows me to "prep" more than one set of equipment to use for the Turn. It does require that I keep track of which way the cars in each track are going since I reuse the Fiddleton tracks for the Turn's return leg, but the cars will have destination tags on them to help keep things straight.

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Next, I then needed to create the Turn. ?I made 3 Turn trains (named A, B & C) and they all use Route 3. ?And each time I build one of them, I get to choose from which track in Fiddleton they leave and to which they return. ?The first time I built a Turn, it found no cars to bring back (I had forgotten to "prep" the spurs at the Creek) and so I had to send it back to the pigeonhole with just loco and caboose. ?But after that, each time I had a Turn ready to go, it managed a suitable exchange of cars at the Creek and terminated back into Fiddleton just fine.

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The final train needed was one to move the cars back to Pigeon Hole from Fiddleton. ?This one I named "Fid-Pig" and it uses Route 2. ?Again, I can pick which set of equipment in Fiddleton to put "away" and likewise, to which pigeonhole I wish it to go. ?If I have multiple tracks/trains in Fiddleton ready to put "away", I build and terminate this train until everything is parked.

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So there you go! ?A working version of something kinda close to what you expressed wanting. ?And, although I did not test the next evolution (with Transfers as you mentioned), this setup can be modified with little trouble, to accommodate upgrades and changes...

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Happy to help, hope it helps,
<Pete Johnson>