If you want the lowest possible seat mounts you can use angle steel to custom fabricate your mounts.
Check out my custom Ultra-Shield set up. I did need to add spacers (I stacked three 3/16 steel plates) on the left side bolts because our floor is not level. Although my setup was a bit more complicated because this seat is bottom mount in the rear and side mount in the front. A true side mount should be easier to make.
I also made a custom back brace (because it is an aluminum seat) but that is a whole different subject.
