Here is the simplest, easiest, and fastest fix..............

<span style="color: #ff0000">Use more rudder during your turn</span>.

Easy as that.

What it sounds like to me is that the tail volume is not quite right for the size/design of the rest of the airplane, so the tail is dropping when in the turn. You mentioned that it looks the same as a Cub, well, the fix for that problem with a Cub is to use more rudder right??? So, do the same with this airplane.