I tried the DIY on seat lowering, but found it uncomfortable because:
(1) the front of the seat bottom is much higher than the rear, resulting in a strange driving position;
(2) the seat back and bottom no longer meet, causing a little pressure on my ***, as it now sits slightly farther back than the seat back is designed to allow.

Which leads me to my question-- has anyone tried aftermarket mounts with the stock seat to gain a little space?

Thanks,

Pre-responses:
I. Yes, I have searched.
II. No, I do not want to switch to an aftermarket racing seat (air bags are important to me)
III. No, I cannot just lean back the seat to get clearance for my helmet, as I have short arms and long legs.

 

You won't get an aftermarket mount that is as low profile as the stock bracket. So mounting the stock seat on an aftermarket bracket won't give you more headroom....likely a lot less. ( and likely won't work anyway)

 

Even if I am willing to forego sliders (i.e. a fixed seat)?

This gentleman had a similar idea (to remove the RX-8 seats from the sliders) but bailed halfway through the video:

 

easiest way to figure it out is to unbolt the seat and have a look at what you have to work with. The floor brace that crosses at the front of the seat bracket is the biggest issue

 

Nothing a hammer can't resolve...

(No, I'm not kidding, this is how I got my Corbeau low enough on sliders to fit me in my helmet.)

 

Ah yeah I see the crossmember you are talking about: http://speedhunters-wp-production.s3...012/05/rx5.jpg

Looks like some people have completely removed it as in Arca's TA car.
https://www.rx7club.com/attachments/...psad24057c.jpg

Wonder what that does for chassis rigidity.

 

If you're concerned you can cut it out and fabricobble a brace that will work with your seat mounting solution.

Or just be like me, throw caution to the wind, and hammer two channels into it to make room for the rails.

 

You can also do a foamectomy on the seat bottom foam. Benefit is better lateral support