Hi Barry,
Increasing the wing size will not affect the flight characteristics in any no ticable fashion; it might be a tad more stable. You can use just about any mini-servos you want. I guess one major question is what material are using to build with (e.g. foamboard, FFF/BlueCor, Depron)? If you go with foamboard the all up weight will be the highest. The airframe will be very strong with foamboard, but this airframe is quite resilient with lighter materials and I would recommend going with a lighter foam unless the finish is very important to you.
I am going to assume you are using FFF or Depron and suggest that you can use small servos like Hitek HS-55's or the like (shockflyer size). The motor can be any cheapy motor you may have laying around (e.g. brushed on a gearbox like those provided with most flat foamies, a small bell outrunner, etc.). On a FFF version (with a 3" longer wingspan) we were using a cheap $8 "bell" outrunner (e.g. Tower Pro 2408-21T-3) on an old used 15 amp ESC (could have used a 10 amp), using a 3s 1200mAh Lipo turning a 8 x 6 electric prop and had way more than enough power and 20 minute flight times.
I would also recommend (if you have two spare servos to use) leaving out the dihedral and "reflex" and just cut "barn door" ailerons into the wing. Double side tape the servos under the wing and use a simple strait pushrod linkage. You will be able to get barrel rolls out out of it, fly quick when you want to and slow her down to a walking pace when you want.
With about an 5-8mph headwind, I cut the power and let the prop "windmill" from an altitude of about 25-30 ft and just held up elevator and she made a slow, stable, controlled descent vertically. I probably could just let it land like that but I always give it a tiny burst of power to stop the vertical drop at around a foot off the ground. She will pull a foot or two forward and and set down just like that.
Shoot me an email at
mudduck@optonline.net if you want a drawing that roughly outlines the aileron cutouts.
Greg