Thanks for the thoughtful reply and insights. My experience in this area is limited to my Ultra Stick Lite that allows throwing the mix switch and coupling the elevators and flaps (opposite movement) for more pitch control perhaps 20-30% more so even with good size flaps, the pitch control is certainly far less than would be afforded by elevators.

My new radio has a additional trims one of which provides for trimming ailerons up and down, which doing so usually requires a corresponding elevator trim... so there is little doubt that elevons in that config would provide some pitch control... the question as always is adequacy.

My freeflight guru friend is suspicious that without any dihedral, the pitch control needs will be more demanding than afforded by such a config. Another config would be to put the elevons on the tail where no doubt pitch control would be adequate, but would roll authority be adequate... again he thinks unlikely to wit I tend to agree on not enough surface and not enough lever arm with them inboard.

What I've concluded to do... is to mount three servos two on conventional ailerons and one on elevator with the first task to determine the airworthiness of the glider for launch. I've used two inch wide strapping tape top and bottom spars and it firmed the wings up a great deal to the point I think it'll be ok. I've added 1.25" strip ailerons and have yet to do the elevator.

This config can test a wing elevon config by then setting it up for three ch with the elevator for back up authority.

The answer will be interesting.