Sounds like your having fun with it... It's a heavy ARF.. That's why I chopped the cowl and put the .91 in it.
I have a couple of the Saito .72's and am running APC 13X6's on them .. I think I could get better pull with
them if I used like a 14X4 but I don't have the ground clearance to do it.... From what I read on the Horizon
site the 65,80 and 91 all use the same case... You might still have the length problem with the 80..