Steven,
I've used Michaels method and its an easy way to remove the gap. It also lowers the pilot. Michael I'm not sure how lowering the engine and coupler affects you, but for me some two rail cars the couplers are a little off.
The only problem for me is the permanent change (damage) and if you lower it too much. So now I add plastic angles for fill. I also apply piping which adds detail. The photos below illustrate. I use Gorilla glue which bonds very well to styrene and engine. A little paint and you would think the manufacturer did it. If your track is not perfect, the truck may rub it and they will eventually break off. I have had one break off. I glue it back on and grind some of the plasitic to make more clearance. I have the process down now, and it takes about 30mins.
3/16" evergreen angles cut to length.
Glue with Gorilla glue and hold for 15sec
Add piping (use glue), can't remember size
Paint;
Before
After
A few other engines I did
Another
Cool huh?
These were screen shots from video I took. If I don't add this to the next DVD I will eventually post on my website.
Rich
www.toytrainsontracks.com