How thick of a head gasket will drop 1/2 point?

I have GT40p heads on a stock '89 5.0 block with 0.39" gaskets. I hear the compression with this combo is ~9.5:1. I have a supercharger and would like to be at ~9:1. How do you figure out the head gasket thickness to lower compression that 1/2 point.

Also I have a locwire reciever groove for Felpro 1006 and don't want to go though the trouble of removing it. Any recomendations on thicker gaskets that work well with the groove retained. I was told that copper gaskets work well with the groove. Is there a downside to copper head gaskets?

GT40p heads are 58-59cc right?

Stock heads are 64-65cc right?

Difference is 6cc.

Felpro 1006 are 8.7cc.

So, if the above is correct then a 14.7cc gasket would be good.

Anyone know if SCE Titans are good?
They make them in a couple sizes that are close.

15.3cc -
http://store.summitracing.com/partdetail.asp?part=SCE-T36067&autoview=sku

Says it needs oring. Is that the same as the lock wire?

13.7cc -
http://store.summitracing.com/partdetail.asp?part=SCE-T36156&autoview=sku

After talking to Cometic and SCE I am convinced that the reciever groove must be taken off. Even thicker gasket now!!!

I am not sure which gaskets I like better the MLS or the self-energizing copper. I am leaning towards the MLS because of evenness of torque distribution. I am a little concerned about the <50ra surface finish requirements though.

Can someone confirm the cc numbers for the GT40p heads and the stock mustang heads?

Thanks.

Here's a pic of the reciever grooves. 4.125"ID, 0.010"Deep, 0.085"Wide.