Ineed frame tie advice for the '67 fastback please!

I had to do about 8 hrs of cutting and grinding to get them up against the floor. Once they are up there you have alot of contact with the floor. When I ran my e-brake cable I ran a tube through the conecter at an angle for the cable to run through. I would think the car would have to flex alot to make the floor brake away at the welds.