approx. headroom gain? (sparco seat and memoryfab brackets)
 

so i am considering purchasing a sparco sprint 5 seat, and memoryfab superlow brackets. i am doing this because i can barely fit into the car with a helmet(helmet rubs on the roof).

What kind of gain in headroom could I expect from a setup like this? i am hoping for about 2"

i'm considering getting the memoryfab s68's with their dual locking sliders. I would hope to gain 2 inches but don't know.