Vertical cg?
that is a puzzle -
When we do setup hover tests on foamie electric monoplanes -which typically have 0-thrust and common thrust/wing /stab c/l, we find the model does pitch down -as noted .
however the vertical cg is just below the wing.
If we hold the model right on the le of the wing - , it typically takes a couple of degrees of up trim and right rudder to get a "balanced " hover --against the fingers.
It almost sems that good old prop spiral flow is at work here - what do you think?
This has held true on dozens of these little buggers we have done.
Flight trimming is another thing altogether and that sorts out easily.
But - this static condition is interesting