Driveshaft enclosure. When is it needed? CHASSIS BUILDERS HELP

Guys,

I have some 2x2/2x3 frame connectors that run from the firewall top the rear 4 link crossmember. There doesn't seem to be any support or strength to keep the connectors from moving around under power or during an accident. All I have tieing them together currently is the trans crossmember which is removeable. I'm looking to put an "X" between the frame connectors from the the trans crossmember area back to the rear crossmember. What size tubing should I use? I also plan to mount the driveshaft enclosure off of this as well.

I would do the "X" out of 1.25" tubing. .065" if it is chromoly, or .120 if it is mild steel. This will be the perfect place for the driveshaft enclosure to be attached to.

Thanks Curley. I see you made it over from the Bullet

The SFI 25.4/25.5 mild steel specs call for a minimum of 1" x .108" wall ms tubing when/if a center "X" is called for between the frame rails back at the main hoop/4-link/ladder bar crossmember. So for a non-SFI combo, using tubing starting at that size range (or bigger) would probably be OK.