http://www.sr20forum.com/gallery/data/529/medium/seat_assy_comp_.jpg
Here is in my estimation, the right way to safely mount your seat. The main rails attach to the cage. We cut out the wimpy sheetmetal stock crossmount and made this stronger one with a wide footprint made of 0.120 steel. The sliders bolt to the nuts welded inside of the mount rails. The harness eyebolts screw into the main rails as well. The whole assembly is sunk into the floor and moved 4" more inboard to give a little space between the seat and the side of the car.

http://www.sr20forum.com/gallery/data/529/medium/gussets_comp.jpg
Gussets reinforce the rails juncture to the cage lower bar.

http://www.sr20forum.com/gallery/data/529/medium/seat_rail_cannel_comp.jpg

Detail of the rail sunk into the floor.

The seat is still too high, we are going to weld the mounting tabs right to the sliders. I think the
B15 has a weird lumpy floor and its hard to get it low. The Sparco seat has like 4" of foam in the butt. Going to try to cut that down to about 2".

Richie's sweet work again!

We did the same thing with the P10. The seat is far enough over that the shifter is right in front of your shoulder (instead of off to the side). This is more comfortable anyway, since most of us lean a little to center on the shifter.

The only difference is our rear rail goes all the way across from the frame rail to the exhaust tunnel as well.

sit in the seat w/o the foam? should get you very low although uncomfortable

Idealy get some expandable foam and make your own seat insert, doesn't look as pretty, but it is a whole lot more comfortable, and you can mold it to sit wherever you want. Make it thin to sit low and better feel, or make a booster seat if needed :)

With a fiberglass or carbon seat, just sitting in it with no cushion is still pretty comfortable because it is countoured to your hindquarters. Metal tubular seats, on the other hand, suck ass for that.

Are you having issues with headroom Mike, or is this and effor to lower CG?

With a fiberglass or carbon seat, just sitting in it with no cushion is still pretty comfortable because it is countoured to your hindquarters. Metal tubular seats, on the other hand, suck ass for that.

Are you having issues with headroom Mike, or is this and effor to lower CG?
To lower the CG since I am the second heviest part of the car. Also to accomodate Tom Paule as he might be my ringer driver.

You going to be able to see over the dash meng? :D

I did mention a booster seat :D

You going to be able to see over the dash meng? :D
There is no dash and the seat is pretty high.

take the cushion out and apply a thin layer of tempur-pedic mattress?

No dash at all, or a custom Al one?

No dash at all, or a custom Al one?
Just a pod on the steering column to hold the Racetec electronic dash and some switches. Maybe an aluminum or carbon cover from the dash bar to the cowel.

Yeah, going to need something to cover up the ugliness there and tidily hide all the wiring, etc.