old bird:
No mods to the box were necessary for my .91 four stroke. I cut the center out of the mount so that the engine could slide farther back. The carb is about the thickness of a nickel away from the wood on the box. Everything lined up nicely.

raymondcz1:
With the .46 2 stroke up front you are gonna need a boatload of extra weight. I have my .91 fourstroke, 5 cell 2300mah AA receiver pack attached on one side of the engine box and on the other I have another AA 2300ma battery for my on board glow. It flies like a dream and lands like a trainer. The CG on the instructions was actually pretty close. You have to balance the plane upside down without fuel. You can use your fingertips on the marks you create according to the manual and get close enough. I would dump the stock muffler and invest in a aftermarket pitts muffler (preferrably one by Bisson). Good prop for the .46 is a 11x5 or 11x6. If its a new engine I would run the 11x5. It will be easy on it for the break in and will give you extra thrust. The gear blocks in the wing are strong. The gear itself is soft. I bought some 3/16 stainless steel rod from the hardware store and bent a new set and added about 1/2" of extra length for more prop clearance. They have worked perfectly. I may be wrong but it sounds like you are new to the hobby. Which is great. If so my best advice is to have some patience ( I know I hate that word too) and put this plane aside until you have a few other planes under your belt. Although this is (in my opinion) a nice flying warbird it is still a warbird and I would recommend this be a 3rd plane after you master flying with a low wing trainer. And if your gonna fly it anyway......good luck and post some pics! I never was good at telling people not to fly. Hee he he