Hello Jim,
I have been a scratch builder for years mostly from plans and I lean toward the more off-beat subjects [ then I take liberties with the looks and design ] in an effort to come up with "something different"

Your best bet is to make a small model of what you want to build, like a glider, cut it out of meat tray foam and start chucking it around experimenting with the cg and control surface deflections.

Most of the "far out " designs like the flying STOP SIGN & lawnmower started out that way, I'm sure.

Start with a flat disc, put some small weight at the front, put some reflex [like a small elevator turned up ] at the back, and a vertical stab for stability, then start throwing it around to see what you got!

Don't expect instant success but keep trying and you will be rewarded that [ You did it yourself ] and you will have the only model like it at the field, while everyone else are flying 'SHAKE & BAKES" This is such a great hobby!

Good luck ----Roger