Today was the big day, and I can report that it flies great!!
Very lively, but also very docile, in other words close to ideal! Landing it is a cinch, although it seems to glide forever in ground-effect. Very stable directionally as well.
As planned, we tried it in glider mode first. Since I had an experienced launcher, he was able to warn me to move the CofG slightly forward BEFORE launching it, by running and tossing it up and catching it again. We did, and everything was smooth sailing from then on. Three glides, fit the motor and flight battery, check the CG again (needed 10 grams extra in the nose) and launch! One or two clicks down trim and she was fine. Ample power from the S400 / 7.2 V and Guenther prop.
Rolling is barrely, but I do have some asymmetric dialled in.
Picture below was taken before flight, smile was bigger afterwards