That's why I suggest the 45. From straight down it has nowhere to tuck to. But Dick is right, A scale model should at least show signs of trying to pull back to level from a dive like that. You're either tail heavy or right on the dangerously neutral point.

The point that Dick and I have been trying to make is that it is still possible to trim a tail heavy plane for level flight at one airspeed. But it's what happens when things change that determine if you have a positive or neutral or negative pitch stability. Trimming for level flight at a cruise speed and pushing it into a dive and releasing the stick is a great way to see what it does with the extra speed. A properly positive stability trim will use the extra speed to pull the nose up and return to level flight. A neutra model will continue at the same dive angle while the speed continues to increase. A tail heavy model will tuck the nose because it required negative decalage between the wing(s) and tail in order to balance out the rearward CG. In this last case with the extra speed the tail lifts TOO much and it pushes the nose down.