My recently purchased MGH bass tends to dive the neck and hangs too far to the left in an uncomfortable position. I noticed both, but bought it anyway.
A piece of titanium (2.2") with two threads relocates the front anchor point for the strap and neck diving is gone. The playing position is much more comfortable than before.
The titanium is freaking ugly, but it serves as proof of concept only and is not intended to be a final fix. I will replace it with Mokume soon.
The belt thing doesn’t work for me either since I practice mainly in sweats, shorts, or my undies. The only bass I have that has neck dive is the Hofner, and I’ve learned to live with it, so it’s no big deal for me.
I found that a wide 4 inch wide strap with suede on the inside would hold the bass in position no matter what I did. It almost seems as though the suede sticks to you. I think there are several on the market that help prevent neck dive and are constructed in this manner.