When I did the main gun on my hetzer I built a frame to give me Traverse and a trunnion that locked over the barrel of the 50 caliber paintball gun, but something tells me that in that scale you're not going to have quite enough space for that. Bwahaha
Seriously, though, it's looking really, really good. Are you going to do the sliding cover that goes on that vent directly in front of the muffler? They made quite a few changes in that area over the few years that the tank was in production, and I know of at least three different exhaust systems that were installed on those. Mine is very similar to yours, but it has the protective screen that goes over it. I like the way yours looks, it's very smooth and looks like it just came out of the factory. Great job.