You have better throttle resolution using a smaller motor that isn't so overpowered. Why not strap my MVVS 1.6 gasser on the front of the plane? It only weighs a few oz more than a 1.2 4-stroke...how about a Saito 1.80...now that's power....
You see, that can go on, and on, and on. I for one love flying planes with more than enough power (2:1 thrust to weight ratio on my latest electric balsa kit build) but there is such a thing as too much IMHO for a glow plane.
Anyone got a 15lb turbine I could borrow?