hi mate dont put a 25 on it!!,that plane looks ideal for a size 10!!.even a 15 would make it verry fast ,i have a mustang with a 40 "wingspan a scratch build that weighs 2 lb 12 ounces and has a size 10 in it.its plenty of engine so im sure a 10 would be a great choice for yours too.lmao at a size 40 been suggested my god a size 40 would be way too big for it!!.