Boxing the engine back was the most difficult part of the build. It worked out very well. The JB weld is getting really hot, and the junction where the copper tube connects has failed, after around 4 flights. But, I ran 4-40 bolts in to secure the copper tube. I need to wire tie the heads of these bolts as they have worked out some. I only noticed this after the last flight, and have not gotten around to working on it. The vents on top are really working good. I know my engine is getting hotter than would be desirable, but it is acceptable, as it is not overheating. I baffled the air flow to direct right through the engine as well. One problem I have had, is I have an air leak where my carb mounts to the engine case. I bought a product called Yamabond to fix this. It is supposed to be the best carb gasket available. The problem is, since the carb is sucking air, I cannot slow the idle speed down far enough to get the desired landing speed I want. Again, I will get in there and do all this stuff some day soon. There are always teething issues with these scale models, and these somewhat complicated mods. One thing is for sure though, mine flies great, better than the first one, so I am overall very pleased with the outcome of that project.