I've had big issues with sparco seats sitting high...
Sparco Circuit in my buddys subaru, this mount was literally tabs on the ground...
in my friends hill climb (exact same seat) EK with buddy club rails we had to take the seat padding out of the bottom and use a mount with no sliders to have a helmet clear the roof...if not you couldnt actually sit in the seat...
in my S14, that seat sat pretty high just sitting on the ground without a mount or anything if you left the cushion in