Mounting race seats is a huge pain in the ass. I need sliders, since my co-driver is 1' shorter than I am, and the setups provided by the manufacturers are utter crap.
My Sparco base and sliders raise the seat several inches, and is nearly impossible to bolt in. My Cobra seat base, which looks to be built much nicer than the Sparco, doesn't even line up so it can bolt in. WTF did I spend my money on?
Here's my tip: don't buy seat bases from the seat vendors. They're very expensive, and total junk. Save your money and build it yourself, since that's what you'll have to do anyway.
Bollocks!