Any feedback?

 

double post

 

or 1.5mm ones? Any issues? Which one is better?

 

Typically, you'd want the thinner of the two gaskets. As for the gasket itself, the Cosworth branded gasket is perhaps (as indicated by pressure testing), the best available.

 

Thanks ^ Do you know why the thinner seals better? I thought thicker is better

 

The difference in thickness is minimal in this instance, but thicker isn't better. One primary concern about thicker gaskets is they move the surface of the head further from the piston deck, and if that space becomes large enough, it increases the chances of detonation. That shouldn't really be an issue here, but the basic point is thicker does not mean better.