F782C cabin center cover needs to be installed to the floor stiffeners with 8R8 screws since the covers needs to be removed from time to time for inspection of the fuel lines which pass underneath.

Vans wants you to have a 15/16" spacing from the top of the F782C cabin cover and the F772 floor skin in view A-A on DWG34.
Well that's easier said than done. You want to ensure you edge distance spacing on the cover but as well on the underlying angle.
Since you slide the F782C in between the floor angle, there's no way to tell how high or low to go.

To make this easier, I pulled out some stock angle the size of the floor angles and drilled a pilot hole on the centerline.
I also marked the horizontal distances on the F782C and a center line on the flange. If you position the parts on the workbench and lift the F782C to the correct height, this is the view you will get:

I also positioned the F782C as good as I could to the floor stiffeners and copied the locations where the holes will come on the floor angles with a vertical line.

I positioned the F782C perpendicular to the floor by holding a piece of angle along the firewall recess and making sure the vertical part of the F782C followed that line straight down.
Well... you'll read below, but that 's what you should NOT do. What you should do is install the fuel valve cover F983C and align the upflange of F782C with the valve cover.

Then drew a vertical line on the location of the hole in the stock angle and aligned it with the line on the floor stiffener end drilled the hole #40

I did this on all 4 hole locations and then brought in the F782C. I made a small woodblock to support the cover underneath and gently match drilled using the floor pilot hole as drill guide.
The heigth came out great in all locations but when I had all holes done and clecoed, I noticed that the fuel valve cover was not aligned at all with the upper flange of the F782C

It's clear that the F782C was too much forward and started thinking of how bad this was ...
On one hand, as I will be using the andair fuel pump with the fuel dog house covering it, I will anyway have to cut off the flange of the F782C and cut out a part of the fuel valve cover as per the plans of andair.
Still I would have some spacing between the fuel line covers on the F704 which isn't really nice so started looking how I could bring back the cover.

The hole is already drilled in the cover and in the floor angle so it's a bit shitty. But then I realized that the hole is only #40 which is the same needed for the nutplate ear on the F782C flange.
I measured the distance between a K1000-8 nutplate ear and the center hole of the 8R8 nut and came out with almost exactly the distance I need to slide back.
So that's a solution. I would put a rivet to nowhere in the floor angle with the manufactured head countersunk on the inside so that it doesn't interfere with the cover.
Now the only thing left to do is to drill a hole perfectly in line with already drilled hole (otherwise would not be able to install the nutplate on the F782C)
I put a cleco on the nutplate and aligned it horizontally. a #30 drill fits perfectly in the nut of the K1000-8 nutplate so that serve as my distance template.

Drilled all 4 like this and now, it comes out perfectly. Phew...

Put the dog house cover over which makes it look really cool.