Thanks for the excellent explanation and links on setting the CG for thermal gliders, Ed. Much appreciated.

I've noticed the main wing has several degrees of positive incidence (it also has a down-turned bottom foil - neg. camber?). I've never flown an airplane that didn't have a symmetrical or semi-symmetrical airfoil. I imagine this is what gives the Radian the excellent lift to drag ratio at lower air speeds.
However, your suggestion of putting the Radian in a 45 degree dive to check for elevator trim doesn't sound like it would apply to the 'Radian' type airfoil - would it?