Thanks for the input, forunately you're right it is "only" the throttle, and this speed control does not seem to arm until the throttle has been cut.

Not enough space in the fuse to change sides on the servo on the glow plane and it's not enough of an inconveniance to justify spending the time to move the servo this late in the season, when I could spend that time flying instead. Not to menton that a computer radio on the way within a few weeks and that'll solve the problem anyway.