Adam,
Thanks for the compliment. I just used a Dremel Tool with a small 1/4" sanding drum to gradually enlarge the opening till it fits just right. It isn't difficult really, just takes a lot of patience. The Magnum 40 is running pretty good with this plane and I really don't have any complaints with it's performance. It's not going to outrun a 60 in the straights, but it's still pretty darn fast. It's pretty funny to blow by some of my friends in their giant scale whatevers and I've earned the name flash. LOL Anyway it's a good "goes where you point it" airplane. I still use the stock tank but I usually only fill it just over half full. I usually get about 15 minutes of full throttle stuff with that amount.
Bud