Scaling up or down is always challenging. I have a paper Fokker Dr1 that flew well at 1:24, it was actually the first paper AC scale model I tried to motorize - way back at the turn of the century (love saying that). It would not fly at all scaled down to 1:32 - too much drag. However, I have a half dozen WWI biplane fighters that work just great at 1:32. All are biplanes, I think it's the small space between successive wings that doomed my 1:32 DR1. (See the following link for some of my 1:32 WWI and 1:48 paper gliders :mrgreen: http://www.zealot.com/forum/showthread.php?t=169146&page=2 The Se5a is 1:24 and I have a lot of experience gliding it at this scale and also at 1:32. It performs very well in both sizes, giving a glide ratio of about 8:1. It is very docile, flairs nicely when it enters ground effect. Admittedly, the wing loading of the RC version is about 21% greater than my gliders. I tested an up ballasted glider version this winter and it performed about as I expected, faster, but still about 8:1. I didn't get many flights because bad landings on hard wood floors were murder. Wing sections that would never do in real airplanes work just fine for me at my small scales. As is so for many of my models, I use a semicircular cross section for the top of the wing and a flat section for the bottom. It's easy to build and is reasonably efficient - Clark-Ys don't seem to work any better for me at this size range. About the only time I don't use it is when aesthetics take over. I don't know as much as I'd like about where the center of lift is in my semicircular section wings. I believe it's well back from the quarter cord, possibly quite near the mid cord. The limits of permissible CG in your drawing are about the size of my uncertainty! In practice I ballast my glider so the cg is about midway between mid and quarter cord and just play with my bendable elevators until the things glides nicely. The little gliders are so light they are practically indestructible if flown over a mowed lawn. Trial and error suffices, I start with a bucketful of up and work my way down. Frankly, I'm pleasantly astonished at how durable my 42.5 g RC version is over grass. Three crashes, just little rip. Once I get the elevator deflection limits right, I'll probably just try putting in successively greater down trim until the model takes off without climbing into a stall. I really need to find somebody to do the hand launch - it takes too long for me to "climb into the cockpit" when I have to do it all myself.