Problems with tailsitter-plane configuration

Hi! i am trying a tailsitter drone with 2 motors (without tilt rotation)[servo function 73 and 74] and 2 ailerons, that works as elevons [servo function 77 and 78]
Issue details

My problem is when I tried to fly it, in Qhover mode (or QLoiter) it is super instable.

What I see, in FWBA mode (like a plane) when i move the controls in my RC, the elevons move normally.
But when I put QHover mode, if i move very little the rc control (like 1% or 2%) it is translated to a huge movement in the elevon (like a 60 - 70 %)

How can i solve it?
Version

3.8.3
Platform

[ ] All
[ ] AntennaTracker
[ ] Copter
[X ] Plane
[ ] Rover
[ ] Submarine
Airframe type

Tailsitter
Hardware type

Pixhawk
Logs

i don’t have log for the moment