I did a few home brew braces to my car- I want to get the control arm braces, and I still need to make a rear frame brace as well.
These are my back seat braces- used 3/4" wide x 3/16" galvanized steel flat stock
These are my radiator support cross braces - used 3/4" wide x 3/16" galvanized steel flat stock and front frame brace is 1/2" or 3/4" black steel water pipe with ends flattened
My core support to fender braces are the factory 5/16" or 1/4" (whatever is) round rod style, not the tubular ones- I need to make some new ones.
I am not sure of the effectiveness of the flat stock as bracing, but my thought on it is that it will keep the core support and back seat from pulling diagonally, but it is not resistant to being pushed- if that makes sense. Since it is diagnoally, one brace will be pulled at all time, so the pushing force isn't as important.
I still need to make a rear frame brace, and I want to weld another bar into the jounce bars in the front as well.
Most of my body mounts are hockey pucks from previous owner and several of them sre severely cracked.