Technical Looking for seat support structure ideas

My last post on this forum dealt with questions about narrowing a '40 Ford hood to be the boat-tail back end for this project and I had a lot of great input. At some point I realized I'd better figure out the p***enger compartment, so I switched gears to that, but then life got in the way (is still in the way) and I'm having a heck of a time getting back to this beast. I made some good progress repairng & modifying the original postal Jeep seat - it had some adjustable seat tracks already and seemed pretty sturdy. It will be the driver's seat and this will be a right hand drive (RHD) vehicle.
I'm now at a point where I need to engineer the support structure for that seat as well as a stationary p***enger seat. Since the cabin will be pretty narrow, I was planning on the p***enger seat being mounted a bit further back than the driver. I think this will add to the general 'theme' of a '30s racer where a 'riding mechanic' was common (required for Indy cars).
You can see the original body mounting brackets in the pics. Ideally, I don't want to go much wider than those.
OK, I'm just now realizing I probably should add some dimensions for the frame and seat...
I'll get those added soon.
In any event, I have plenty of structural metal and welding wire for just about anything.
The floor will be a combination of steel or aluminum where feet will go and further back, possibly wood - but that's not settled yet. And the position of the steering/dash support hoop is not final in either shape or location.
My first thoughts were to just run some rectangular supports across the width - maybe welded or bolted to the brackets directly or with rubber donuts of some sort...
I even considered using some lawn tractor seat springs (seen in the pics) but I'm not sure that's a great idea...
All-in-all just interested in folks thoughts/ideas/questions/considerations.

Frame - right side (driver's side) by steveu812 posted Oct 4, 2022 at 5:41 PM

Frame - left side #2 (p***enger side) by steveu812 posted Oct 4, 2022 at 5:41 PM

Frame - left side #1 (p***enger side) by steveu812 posted Oct 4, 2022 at 5:41 PM

Driver's seat sliders by steveu812 posted Oct 4, 2022 at 5:41 PM

Driver's seat by steveu812 posted Oct 4, 2022 at 5:41 PM

 

This is what I did for the floor in my Studebaker truck.

 

Plus the seat belt mounts worked out easy.

 

Thanks. This helps a lot. Seeing the way you did the "arch" undeneath - I think that's what bugging me - I was concerned the center would be under supported. I have plenty or room to run something similar to the lower part of the frame.
Is your seat superstructure welded or bolted to the frame. I welded my engine and trans crossmembers in, but from there back, it's the factory rivets which I suspect will provide a small amount of give. I'm not going to be racing or off-roading in this so my only concern with frame flex is the possibility of weld fracture - especially in the middle where it will twist in opposite directions.
Thanks again - This got my mind going with ideas and I'm hoping this will stoke my desire to carve out more time for this project!

If anyone else has some similar ideas I'd love to see them.

 

It is bolted solid ( no type of rubber ) there are six 1/2 inch bolts on each side.

 

Wow - twelve 1/2" bolts - that's a super-duper structure.
Thanks agian for the input, I was looking at the frame again last night and now have some ideas rolling around in my head.

 

Here's what is in the Whatever project. Bolted to the frame rails and the seat backs tie into the roll bar support hoop. Haven't bought seat belts yet, but I'llbe doing something similar for mounting points.