Funny thing with this Giles is it is only 4" short of the GP extra wingspan and the extra calls for a .90 2 stroke up front or a 1.20 4 stroke. I have both and the extra is a better setup more forgiving plane, but the weight difference is minimal. I have a .91 4 stroke in the Giles with a 13-8 simitar on it and it will hover but barely. I tried a 14-6 and it didn't do as well. granted the engine only has about 5 tanks of fuel through it. I would look at a .91 2stroke or a 1.00-1.20 4 stroke for unlimited verticle for the giles. God knows the cowl is big enough for either.
Jeff