Paul is probably right about there being little need to compensate short wheelbase vehicles - that is provided the axles are parallel in all planes (across the vehicle and along the vehicle) and that they are perpendicular to the direction of movement and to the potential buffing and coupling forces.
It is also important (in the context of most of our NG stock) that buffers are truly central on the end of the vehicles and that they, too, are parallel to the direction of travel.
Both conditions are particularly important when vehicles are being propelled.
Empirical evidence gathered by my friends Chris Pendlenton, Bob How and Mike Clark (Masokits) working with pinpoint axle/bearing fitted S4 wagons and carriages, demonstrates that a fully sprung vehicle rides better and runs further than a compensated vehicle and that the compensated vehicle is better than a rigid vehicle.
The 'experiment' used straight, level track and a free swinging, cushioned, pendulum to deliver consistent impetus.?
The perception that NG wagons rattle and bang along is, I suggest, largely based upon observation of unsprung waggons and skips.? Those vehicles that were sprung, such as the L&B wagons, getting back to David's enquiry, probably only rattled a little when they were empty and their springs virtually uncompressed.
My personal instinct is to spring vehicles that were sprung in the prototype, if it is at all possible.? It is a challenge and a chore but the silky smooth passage of said vehicles is a delight to watch!
Adrian
Adrian Gray