Don,
Just saw your mail from the other forum about your MTH 0-8-0 and thought I'd post here.
Sorry it took so long, I haven't been on that forum lately.
On my MTH 0-6-0, I dremeled out the cast-on coal load (die cast tender) and made a styrene floor along with a black foam rubber coal load to replace it:
The charging jack is underneath, mounted on the floor. On my other installs the on/off switches are mounted so that when turned on they point towards the front of the engine, but because of lack of space on this tender, I had to turn the on/off module around to make it fit and have enough space for the battery. I may eventually try to relocate the charging jack (wish the water hatch opened).