I'm copy pasting what I wrote on an audio forum completely forgetting maybe someone here may have more experience with the platform.

I'm bummed I have to ask for help but I find myself just totally lost. There is nothing for me to reference in my car for mounting points. I want to use the stock location, but it's hard to design a mount. The bottom floor isn't flat. The left wall (towards the quarter panel) is not flat. Without two points to create some "squareness" it's hard to engineer a mount. What's worse, is I also have two pieces of equipment from the car (radio and navigation module), and the navigation module can't be mounted vertically because of course it can't - it has a CD in it. It's also poorly shaped because the wheel

Here is everything I have to mount:
Stock Radio (7.375 x 6.5 x 2.375)
Navigation Module (7.375 x 6.5 x 2.375)
JD 400/40 4channel amp (9.5 x 7.5 x 2.125)
Alpine S-A60M (8.0 x 8.125 x 2.25)

The stock mounting isn't ideal.
It has a tiered shelf, pictured below. The radio sits in the middle of the vertical mountings, and the stock amplifier mounts to the far left/quarter panel, but the stock amp is 1.375" thick. When mocking in the Alpine amp back there, it would touch the chassis. When mocking an amp in the most inward position, I'd have to do a lot of trimming if the metal bracket and there still isn't a home for the second amp. Also, the amps would be stuck below the navigation module, which would potentially trap a lot of heat.

I proposed a new design where the radio and navigation module where would be stacked on top of each other horizontally and then have the amps on top, mounted vertically. Each of the amps are roughly 5lbs, so that's 10lbs mounted vertically. I track the car, and in my last track day I was holding 1.3 sustained G's (Laguna banked after the corkscrew), so that mount front the horizontal section to there vertical has to be sturdy, but the weight of those amps will have so much leverage on the mount. I just don't know how to go about this and am tempted to take it to an audio shop. That would just feel like defeat and ANY help from an overall solution to designing one would be appreciated. If I could cut and bend sheet metal, this would be a slam dunk.

images including my mockup design: https://imgur.com/a/sq87wzi