Rollcage question-lateral supports

In order to certify ,what do you guy's have your rear lateral support bars welded to? The S&W website where I plan on getting them from shows them welded to a floor plate but someone suggested cutting a hole in the floor and welding them to the frame connectors. This is for a 70 B body running 8.50 and slower certification.
Thanks Mike

I'd go down to the frame connectors. Maybe even X them so they go to the opposite frame connector.

Mine land on a plate welded to the top of the ladder bar brackets. Transfers the load into the entire cage structure. 8.50 cert. Been recerted twice to boot.
Doug

Mine are welded to a plate right in the corner of the floorpan and driveshaft tunnel.

Thanks for the reply's. Will it cert with plates?
Mike

Yes, mine is NHRA cert'd to 8.50. Well, it's expired, but it certified no problem in 2008.

As far as I know, welding to plates will certify no problem. The certification is to make sure if you wreck the car the cage will protect you. BUT, you install a cage for two reasons, safety and strength of the chassis, by welding to a crossmember, or the frame, you increase the stiffness of the chassis, a lot more than plates on a sheet metal floor pan.

The solution pictured makes me a bit uncomfortable concerning based on what I see, with the bent ends on main bar x brace, and that the bottom of the main roll bar and the x brace ends are not substantially tied together, which makes for a weak design load path for any side impact loads on lower main roll bar. Might certify fine, but IMO, a lacking solution.

Plates on the driveshaft tunnel are legal. I much prefer frame ties sectioned into and welded to the floor with "outriggers" from the framerails to the rockers also through the floor. Then the main hoop and diagonals set directly on those frame pieces. This rather than floor plates.

And Xs and triangles are your friends in your efforts to stiffen the thing up.

The outriggers tied to the inner rocker is stronger in my thought. I plate the inner rocker as well. Cutting the floor out large makes full welding access easy. The removed portion is easily trimmed and welded back in to fill the hole. Subframe connectors are welded solid to the entire floor pan. Even with stock rear rails the chassis remains stiff. Always leaves level with no twist. Has been numerous 1.25-1.26 60 ft off the foot brakes on 10.5s.
Doug

I built my first 8.50 cage this year. I also used an S&W kit, Chromoly to boot. The best call I made before the build was to our division NHRA chassis inspector. I had that guy on speed dial and he was happy to answer all my questions. By the time he came to certify the cage it was a matter of formality. No drama! As others have already noted, anytime you can tie directly into a frame component the better, including the lateral bars (referred to as D bars in NHRA general regulations). Cheers!