For the guys that have no clue about what they are talking about. I have lots of experience and the Aviomac 85 twin is the smoothest runner out of all the twins that I have ever seen or OWNED. They may be a little bit heavier but if your building a 33% they`re usually so stinking tail heavy that you have to move everything forward or add weight with the lighter engines. For its size the 85 twin pulls very well and is the smoothest one that I and several others state the have ever seen.