For a 4 stroke, an OS 120 would fly the plane, but your prop size is gonna be kinda small maybe. Im running a saito 125 with a 15x8 MAS propat 8500 rpmson a 60 size 64" wingspan P-51 that weighs 10 pounds.
My CMPME-109 came out to 17 pounds, but its electric so battery weight makes it heavier, but its also spinning an 18x12 prop. Im betting this plane could come in at 15 pounds safely with a glow motor, but, Im not sure Id be comfortable using only a 15x8 size prop. My KMP ME-109 is the same size(73"ws)and weighs 1.5 pounds LESS at 13.5 and is using a saito 180 with a 16x8 prop.

You'll be ok flying, but your not going to get much vertical and it will take you a bit longer to get off the ground with a 15" diameter prop as compared to a larger one producing more thrust. However, if you went to a 16x6 prop, you'll do better with thrust, but your top end speed is going to suffer.