Here are a few shots of the electrical tray I made. I first took a few measurements of that area of the frame, then modeled this sheet metal part in SolidWorks. This allowed me to print the flat pattern of the part and test-fit it as a cut and folded paper sample (see previous images). When the paper box seemed to fit about like I wanted it to, I went about cutting out the flat pattern out of 1/8" aluminum sheet. This was overkill, and I could have used a much thinner material, like .070" or something, but this box will be extremely dent resistant over its lifetime.
The forming of the box was actually pretty difficult, given the manual brake (sheet metal bender) I had access to, and the complexity of multiple internal bends. Again, since I have no ability to weld aluminum, I riveted the corners together. I actually prefer this look to welds anyway. DTT member, fresh_c helped me form and rivet this, as my bends weren't perfect and it took some C-clamps and muscle to get everything to line up before drilling and riveting.
If I can find some images of my flat pattern, I'll post those up soon too.
These mounting tabes were originally made quite oversized, but I waited until I held the box up under the bike frame to trace the tab arcs, and mark the holes, to ensure proper alignment, before finishing their trimming with a Dremel and hand files. The bolts currently installed (up from the inside) are too long, but will be replaced with some with shorter thread shafts, to sit flush with, or below the top plate, as to not make contact with my custom seatpan.
First shot of seatpan. This is .070" aluminum, if I remember correctly. I gave it a slight kink down the centerline to give it a little rigidity before making the other two bends to fit the frame properly. I'll get some better pics up soon.
Now, because I'm a larger guy, and I may end up running 1" shorter shocks in the future (maybe not, we'll see) I wanted to check tire clearance through the full range of motion, so I removed the shocks, slid the rear axle as far as it could go forward in the axle plates, and lowered the bike on the jack until the tire made contact with something.
Although it hits the rear of my electrical tray before touching my rear frame hoop and tail light / license plate mounting tab, it's unlikely that this will ever occur in practice. If I move the axle back 1/2" in the axle plate (usually required to attain proper chain tension) the electrical tray clearance problem disappears, and the concern becomes the rear frame bar, at the 12:00 position over the tire.
My next step is to cut out the necessary area of the seatpan's rear section, and create two crecesnt / wedge shaped side peices and an arced inner fender to create a bump for tire clearance, much like old drag racers would 'tub' their rear wheel wells to make room for big, wide, tall slicks. This will also be riveted together, with the heads of the rivets only being visible from under the bike, and maybe slightly from the rear, but unlikely once the tail light and licensce plate bracket are installed.