Hi Clark,
I am a little late responding to this message but better late than never.
I like your extended spindles. I have also machined a new spindle to accept 8mm watchmaker collets and it worked out very well. I use the new spindle for a different purpose and that is as a grinding spindle on a shop built tool and cutter grinder.
Several years ago I saw an EBay listing for a box full of old Unimat spindles and parts so I bought it. It was quite a find and I was able to put together several complete Unimat spindles from all the parts.
Dick
OldToolmaker