After messing around with a bunch of different ideas, I got it to work. The trick is to use the hatch/cabin on the boat. Most of the weight of the hatch is aft of the CG. That is the only way I can get the CG aft enough to be able to get the engine forward enough to have room for the exhaust. I have everything in now, and the balance is pretty much perfect with the gas tank empty. I still have quite a few little minor things that I have to do before the boat is done, but I'm very close. And now that the hatch is going to be on while running, I am going to add a few extra air scoops to try to assure adequate cooling. I'm a little nervous about how close the exhaust is to my radio box, but worst case, I can wrap the exhaust there to keep the heat away. It is looking pretty good, I'm getting excited. I hope it's going to be fast!
To do list:
Permanently mount gas tank
Balance and mount prop (Prather 275 stainless)
Waterproof stuffing tube outlet in hull
Radio box guts- mount servos, connections, mount on/off switch
Add air scoops for cooling
Few other odds and ends...