I'm in the process of creating a new subframe for my Z. I've been reading, reviewing, and studying all the z subframe installs I could find. My latest concern is where the front rails meet the firewall. I've seen some where the frame rail appears to be welded to the sheet metal with another piece spanning between the front frame and floor support right behind the tc bucket, and others where the subframe under the floor pans continue up the firewall and tie into the front rails. My concern now is the front rails are a lot more substantial than what they were. If I were in a straight on collision, the rails, if installed like what I have seen, could be coming through the firewall and into the passenger or driver. I want to put a plate on the firewall similar to the plates used on a roll cage. The front rails are 2.5" .120 wall square tubing. What size plate and thickness would be best for this application? I was thinking of something 6x6 in either .120 or overkill with 1/4 plate.