Dosn't the box say .19-.25? But that was when the kit came out in the late 70's Those glow engines did not have the power of todays engines.
Darn shame the OS .15CV is out, best most powerfull and reliable .15 ever made. I have them on my Stafford B-24 also. In todays world of GIANT who would buy such a small glow engine?
By the way .15 size engines do not stick out of the cowls. So you won't have to butcher those rare spun aluminim cowls.