In reply to Racingsnake :
Stiffening the chassis should do both.
I’m really just starting to research. Here is a thread discussing what the low riders do (with good pictures):
Lay it low frame reinforcement
They focus on fish plating the sides of the X (with 3/16, 1/4, or 3/8) and reinforcing the suspension attachment points.
Here’s a good Hot Rod article which focuses on panning the bottom surface of the X with 1/16”:
(Click on full article and scroll through pictures with descriptions.
I haven’t looked hard to figure out the best approach for me, but I suspect it is a combination