Some pictures from where I left off last Sunday:
It was a battle to get the front edge of the upholstery down far enough to engage the hooks on the frame. As you can see, there is a stitch seam that the hooks are catching. If that stitching wasn't there, the vinyl would simply tear all the way through.
The hooks were originally hammered down towards the front surface of the seat back. In order for me to progress this far, I had to bend the hooks to point out from the frame at 90 degrees. When the hooks get bent back down finally, they will again point towards the front surface. If I did that right now, the vinyl I have holding on the hooks would simply slip off. So, it is important to note that the only thing that holds this front vinyl from slipping off the hooks when you tap them down to their final position, is the back vinyl part of the seat back upholstery.
When the back vinyl portion gets pulled down over the hooks, and they are tapped down toward the seat front, the back will not be able to slip off. The only reason the front won't slip off will be due to the front vinyl being put on first, and thus it will be trapped under the back part... with the back vinyl portion unable to work loose from the hooks.
What I also notice is that the back vinyl does not have any cord, or wire running through the part where the hooks will go through. Because of the high amount of tension, and the fact that "the back has to hold the front also", I am going to run some wire through the back, bottom edge. It is stitched there, so I will be able to run wire through the loop that has been created when the bottom edge was folded over and stitched. With the hooks engaging the wire, the full length of the vinyl material will be holding the seat upholstery to the frame, not just the tiny portions of vinyl which are in engaged by each of the hooks.
To get the back upholstery to where it is now, I had to use the sun to warm it up. While I was doing that, I put the seat bottom in the sun last Sunday also, and it really helped improve the look and fit of the vinyl upholstery on there as well.
I still only have zip ties holding the seat bottom upholstery down to the frame but they are pulled all the way tight, and I am satisfied with the final look here. So, I will put on the hog rings and remove those, and tap down the metal hooks on the frame to finish out the bottom upholstery installation. Trimming the excess "bar" off of the foam front of the seat bottom was the right call:
Hopefully, it will get warm enough today (sun is out) for me to continue.