The C15 locomotive is supposed to go around some sharpish curves but with a short driven wheelbase I've decided that as little side-to-side movement of the big wheels is a good thing.
The kit designer obviously thought of us hard pressed modellers and so filled empty space on the etch with lots of washers. So many I think that I could have reduced the sideplay even if he'd included an N gauge chassis for those O gauge wheels !
Two thicknesses are supplied, full and half etch. On the driven wheels I've used a pair of full and a single half-etch washer. The others just get a pair of full depth ones so we get a fraction of a millimetre of play.
My only complaint is that the middle hole has ended up just a smidge too small. If you remember this then reaming them out a couple of turns while they are still on the sheet is easy. Forget and they are a real bugger to hold. Or you can do what I did and decide there are plenty of spares, I'll throw those two away and do some more !