I'd like to thank everyone who replied to my original question.
I hate taking an interior apart just to paint and install upholstery. So, I've always put the paint and interior in first and worked upward and inward from there. I find that if I'm reasonably careful, the interior does just fine. Besides, touching up a few paint chips is easy enough to do later.
Here's what I came up with for the "console". I'm quite pleased with it (so far).
Hiding beneath the "tunnel" is the boost pump, fuel filter, and wiring (to be added soon). The wiring is easy enough to get through the spar (not shown) on an RV-6. Then it branches out everywhere from there. Getting through the rear spar will require moving over under the seats to avoid the elevator push rod hole in the spar. Other than that, it should be straightforward enough.
I added a couple aluminum angles to make a "Z" bracket out of the existing floor angles. This gives the new floorboards something to attach to. I did this because I've never been wild about the RV-6 uneven floor. My new floorboards do slightly reduce the amount of space beneath the rudder pedals, but I don't expect that to cause a problem. (I may raise the pedals slightly, but it probably won't be needed.)
You can't see it, but there is black, closed cell foam beneath the floor boards. The foam provides insulation and helps support the floorboards too.
I lowered the fuel valve so it wouldn't poke me in the back later when I'm working under the panel. The valve is still in plain site when sitting in the seat, and is still easy (for me) to reach.
Also, I made covers to protect the fuel lines from clumsy feet. Only the loop immediately adjacent to the fuel valve is unprotected. I'll just have to watch the passengers closely and remind them to be careful.
A bit of carpet from Home Depot's aviation aisle is just the ticket. Very inexpensive and lightweight. Yes, it could burn, but I'm willing to take some risks.
The carpet is covered with a bit of carpet protection film, also available at Home Depot. It's like a clear post-it note on a roll. Works great to keep drilling chips from sticking in the carpet. After all, I've got a long way to go to finish this bird.
The firewall is insulated with closed cell, flame resistant foam to help keep the heat out. Once again, yes, it could make nasty fumes if a fire occurred, but I'm willing to accept some risk to stay comfortable. (A propane torch will make this stuff smolder, and it smells bad, but when the torch is removed, the fire dies out.) YMMV, use your own good judgement.
I used my CNC to engrave the fuel valve bracket. It's hard to see in the photo, but nearly nothing of the original Van's fuel valve bracket remains.