who runs 13sec to 12.80 in the 1/4

You may not need the thinner gaskets. It is a combo of piston height, head cc amount and gasket thickness and bore that will detremin the ratio. The gasket thickness is a minor adjustment to the overall ratio.

example, A 360, .030 zero deck 5cc piston relief piston and stock 360, 72 cc heads with a .039 gasket @ 4.10 bore is 10.30 -1 ratio.

Changing the gasket thickness wil look like this;
.060 = 9.81 -1
.020 = 10.80 - 1


Notice there a .040 difference in gasket thickness for 1 point of compresion.

The same above starting example with cylinder head cc change;
72 cc sarts at 10.30-1
72 down to 65 = 11.19-1 ratio.
72 up to 85 = 9.01 - 1 ratio.

Same starting example only with piston height change

10.30 to start, down .050 and then down to .100

-.010 down the hole, = 10.07 - 1
-.020 down the hole, = 9.84 - 1
-.030 down the hole, = 9.63 - 1
-.040 down the hole, = 9.43 - 1

Can you see how wide and varied it can become?
This is why most people here will recomend a zero deck piston to start with. It gets the compresion up very close to where most performance engine will want to start with. It avoids head milling issues that crop up like bolt hole alignment.
There are other pistons on the market that are down the hole .010 to start with.
This is based on the 9.58 or 9.6 deck height. This will also vary. The actuall deck height and what the piston makers bases the piston height on.

Confused? Thats why there machinests. I use'em. He he he. I can't afford the tools and time needed to do the major amount of work needed to build up a ace engine. This is where I am very happy to save and pay for there services.