Let's talk Zagi 400X.

Of course, most of us know it has a tray with a built-in thrust angle as well as a vertical offset for the motor. On my maiden voyage, I crashed hard and ripped the motor from the tray; it was toast. From there on out, I discarded the tray entirely and used the "5 minute motor mount" mentioned on www.yourzagi.com. (greetz!)

After trashing a Wingwarrior Raider panel set, I recently rebuilt the actual Zagi 400X airframe. Worn out from zip ties, I epoxied a plywood transom to the TE. The motor sits directly on it with no shims (lazy). The motor now has a thrust angle parallel to the TE of the airframe. The original Zagi400X thrust angle is negative (pitched nose down vs the chord line) and sat up a bit higher in the tray.

Nowadays, altitude gain is very difficult. Airspeed is always borderline stall. I've tried many variables. I truly suspect my problem to be thrust angle yet there is VERY LITTLE documentation about this critical metric.

My question is- where is the optimal thrust line? Does it have to do with the CG? Does it have to do with the chord line? Can this advice be applied to other airfoils?

Thanks in advance