Struggling with Amp install

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

I'm guess all of those measurements are in inches?

Are you trying to use the stock location and put the carpet back to cover it?

Why can't you use cut sheet metal? Just need an angle grinder. You can bend it too if you're not going too thick. Otherwise, just connect them together with some L brackets.

Honestly, it doesn't look that difficult. I would just get rid of the entire stock mount and create one from scratch. If you want the bottom to be flat for some reason, then lay a sheet over it and use the stock mounting points. I probably would just use a bunch of steel L brackets or some tubular aluminum rods cause they are easier to cut/drill. I wouldn't even bother with making the bottom flat. As for mounting points, why do you have to limit yourself to just using the stock ones? Make new ones. You can drill into metal. I like to use Rivnuts. Drill a hole, insert a Rivnut, now you have a threaded hole lol you can use all of those existing holes that are on the brace that is on the side that the stock mounts use.

Have you already tried doing a mock up of your proposed solution to see if it fits how you want it? Use cardboard, magazines, or something between the modules to keep the spacing similar.