As promised, I've taken some pics of what I've done so far.

Tonight was solely the 56xx. I've long had the body built, honestly to a mediocre standard.

This will be my first locomotive kit, so on this build I'll stand the molded handrails, and the castings that came with the kit. Most of my work tonight was finishing the hole for the trailing axle.

I think I managed to get the hole too high, though; the trailing wheels look to be a floating axle.

The instructions were not entirely clear on the procedure, admittedly. The wheels do turn freely, though, and have a good amount of side-play. I have yet to test the chassis as modified, or with the Langley body mounted. Next stage will to be finess the fit between the chassis and the body; what I had thought was a good fit hadn't accounted for additional wheels.