I'll second the MAgnum .91 I think I am running a 15x4 on mine. It does have unlimited vertical and I actually used the stock mount. Fits better and I have plenty of room on the mount so its not a safety concern that I have seen.

The other thing I have done is strip all the covering off and recover the plane. I had some hangar rash to repair and got a wild hair. I think it saved me some weight, we shall see.

Tom