You really need to take this to the 1/2A & 1/8A airplane forum. Over there we build al sorts of "small" planes and many have done Guillows conversions. I have a 36in wing span Guillows Cessna Skyhawk in the box I plan on using an OS .10 on. I have yet to successfully convert a Guillow's model but it has been done and there are some build threads in that forum. Be careful as these small planes are very weight sensitive. Most will say that the cost of building one of these is such that you could have had a nice ARF. But we do it for the challenge, don't we? Most of all good luck and have fun with it.