Make a backplate for the engine out of plywood (it doesn't have to be any larger than the radial mount). I think I used 1/8. Calculate the length for the standoffs. Subtract the thickness of the backplate. Cut 1/2" dowels to length. Bore through the dowels lengthwise for # 6 screws. Coat the wood parts with thinned epoxy or equivelant (oil proof). Put it all together.

Over heating shouldn't be an issue. There is good air circulation. The wood dowels won't be perfect in length, switch them around to get the proper thrust angle.

If you mount the engine with the muffler down (to help keep the oil off the model) you will probably find that your tank location is too high. The engine will run fine but fuel will siphon and drip constantly out of the carb when the engine is stopped.[&o]