I finished fitting and tacking the four C-channels in place on the bottom of the new floor. It's already considerably stiffer, but not yet ready for any weight. I've braced the floor with a piece of angle iron to hold it flat while I work on the channels.
This week, I finished the welds on the drive shaft tunnel hoops. I cut a few inches from the too long floor to use a a template for fitting the C-channels to the floor and took advantage of the opportunity to see how the flooring might be bent to form the kick-up transition from the floor to the firewall. The experiment with partially cutting the floor and bending the uncut part was successful. I trimmed the C-channel to match the profile of the floor and tacked the first of four pieces in place.
I used some creative clamping to pull the drive shaft tunnel to the partial hoops and placed the C channels alongside to see how they'll look. I tacked the hoops in place. Enough for today; I'll finish the welds later.