Seating / Gas Tank Conundrum

[Xusia]

The situation:

• This is primarily a daily driver.
• I need more leg room.
• I want to have interior storage (for stuff, amps, subwoofer, whatever).
• I want to use the stock seats & belts (because I think they are good enough and they came "free" with my donor).
• I want to be able to drive the car on track for driver training, track days, and high performance driving events (no competition).

Because my Father-in-law can build me a custom gas tank for very little money, I had intended to "move" the gas tank location to the front. This simplified the rear firewall greatly, provided more than enough leg room, and decent enough storage room inside the cabin. Incidentally, this would mean no sway bar for me. I could probably work around it, but it would limit tank capacity and just generally be in the way. Besides, I can get around it by running stiffer front springs (this according to Jim at FFR).

The problem I'm seeing is that because it's a convertible, 5 or 6 point belts seem to be required. I suppose I don't mind fitting them (welding in a harness bar is no big deal), but can you use them with stock seats? For daily driving I'd want to retain the OEM 3-point belts, using the harness only when necessary. If I have to go with aftermarket seats for harness compatibility, I'm thinking I would lose the ability to use the OEM 3-point belts, which I REALLY want to be able to use for convenience. I really don't want to be stuck using a harness all the time.

At 6' tall, I'm also worried that I may not be able to sit low enough with the stock seats and a helmet to pass a broomstick test. I wouldn't mind removing some foam from the seat, if that were necessary.

Anyway, I'm looking for some help & guidance here. Thanks guys.