Re the screw on the front of the diesel: I can't remember the size offhand but it is a tapered coarse thread with a countersunk head. It's pretty short and as you said, you need to be careful not to strip out the hole.
BTW, you can get 0-42, 054, and 0-72 curves in the older style tubular track, and it will be cheaper than any of the new track systems, if you want to save some money. It doesn't look as fancy but it will work fine.
John
