Just had this happen to me this weekend as well. Check the seal, mine had a crack in it. I've been told the Sullivan 10 will fit, but I think I am going to route it out a bit and try to get a Sullivan14 to work. I love to fly the US, but am sick of fixing Hangar 9's obvious flaws. Don't these guys go to the field? I swear I have heard of 5 guys at our field having the front gear ripped off, another couple more with leaky tanks and one guy had the engine mount fail. I really want the Hangar 9 P-51 and have come close to buying it on many occasions, but after all the little flaws in my US I think I will let my pocket book be my voice and just not buy any more Hangar 9 products. Besides, I am really sick of the Hangar 9 / JR relationship. I ask you, how hard is it to make a standard size servo? It bugs me that Hangar 9 makes servo cavities for the slightly smaller JR servos forcing everyone else to spend time enlarging the darn things.