Mine has a saito 150 on it, and I moved the battery 6 volt 1000 nimh all the way back to the tail. I too originally cut an access hatch in mine behind the TE and had the battery there for about a month. I reinforced the cut area with a couple of pieces of balsa across the fuse, and used them to help hold the battery in place with foam and a velcro tie wrap. After going with the 150, I then moved the battery all the way back to the tail Its wrapped in foam, and hasnt moved yet. I used the hole I cut in at the bottom of the fuse for my rudder servo to slip in my battery. The overall weight increase is not too bad witth the 150. this is the third engine I've put on it. I do have about 1 1/2 oz of lead on the tail right now, because I have my tank mounted in the stock location. Once I put either a cline or a 2 oz header tank up front, I'm going to move mine back to on or near the cg. I'm able to get 12-16 minutes out of a stock tank, even more if I'm just putting around the pattern.

I'm able to turn an apc 17/6 prop on it with no problems what so ever. The only problem I've had is my canopy broke during a couple of very hard blenders. So its without a canopy. I havent run the engine too much with the cowl this summer (because its been really hot n humid), but will once it gets cooler in the fall.

Hope this helps.