Last time I built this locomotive kit, there were a few issues with the frames (too narrow) and the axle bearings (too wide). That's all part of the game as far as test builds go - there will be hiccups and you just fix them or find a workaround, meanwhile the manufacturer will go away and sort the problem out. I know everything should be correct first time out but this is real life and it's not. A good kit will have been put together by someone who isn't the designer of manufacturer. Then fettled. All this before the first buyer gets their hands on it.
Anyway, this time I find an extra fret in the box containing frame spacers that are slightly wider than the ones on the main etch. Put these in and the bearings have to be shaved back a touch to the ends of the axles. This is far better than having to use washers to shim away any sideplay.
Better still, the bearing makers got the middle hole right so I didn't have to bush this either ! You might think that this was an odd error originally but it can be easily explained; G1 axles are fatter than O gauge ones and the bearing makers usually work in the larger scale. The trouble is that the axles are the smaller ones as it somehow helps keep the cost down and results in a 10mm kit that costs no more than a 7mm one. Of course you can still use G1 wheels, for example those machined from iron castings, you just have to ream the hole out a bit more.
It's nice to know that the effort on the test build pays off and ruler manufacturers have had two more sales in the Birmingham area.