If I were a betting person -I would bet tha a LOT of the problem had to do with the physical servo/linkage /elevator setup
A good test is to see if two clicks of trim -either way- from center will make some discernable movement in the elevators. also with new GOOD radios - it is almost impossible to fly them easily without expos - the tx/rx and servos now available respond like trained rats - -making shaky or quick stick movements into wild elevator movements.
On my DX7 I need typically 50-70% expo in elev- -on a model such as th H9 Corsair - I would start with 25% expo and do a hi/lo throw setup. (my X9303 needs l a bit less expo)-
Some claim they don't use expo-
that's possible - -but it infers that the setup is either very vague -or slow -or old -or weak -or tiny throws are all that is available.