Allright, today i got 2x 4-point OMP racing belts, and finally recieved the adapter for my Sparco seat.
I installed the adapter, then had to drill 2 holes for the seat in the right position, and put the seat in car. Yummie. Then also installed drivers OMP belts (witch are btw better than Sparcos own belts, because the joints where you can tighten the belt are way better, they dont go loose by themselves).
Also got a pair of the Sparco softening pads, because my right collarbone cant stand much pressure.
Did a little test run, omg i love it, so much better.

Pluss the racing seat is about 8 kg-s. So it should be about half the weight of the original or smth like that.