I built this model and had no particular problems with the kit. However I did have a problem with the engine installation. I followed the instructions and ordered a .40 engine.This engine has a side discharge exhaust port. The muffler could not possibly fit in the engine compartment. I wanted it to look good, and the muffler sticking out of one side looked weird to me. There is also the problem of how to waterproof the cowling. The muffler is large. The cutout for it would be difficult to seaI after it is installed. had written a letter to Dumas asking for some help, and received no reply. This was before the internet, so now we can find better information, I hope. If I were you, I would look for a rear discharge engine instead of the one called for in the instructions. I can look up the engine number I used if you are interested.And maybe you can help me. Is a muffler necessary? Any others with information would be helpful, too. Good luck with the kit, and let me know how it works out.