cometic head gasket issue

has any one else ever used these cometic head gaskets,I just had a 340 rebuilt and wanted to keep the com.ratio under 10:1 well after all the machining was done the trw 9.5:1 pistons were installed the sat .045 above the deck so they used .074 cometic's MLS(multi layer steel) and with my luck they leaked all over on the dyno. my ? is can this leak be fixed with a stop leak of somekind. if so what type would be the best suited for this app. ok so its a 70,340 .040 o/s trw forged,w/27lbs oil ring tension.eagle sir rods.all balanced int.and alinhoned,sqr decked.etc. cam is Custom by cam motion hyd.502/510 w/240-246 duration@50 inst.@106 deg. as for the heads there j castings w/205 int. 160 exh. REV valves,comp cam springs,ret.& locks controlled by pro magnum roller rockers @ smith bros.pushrods the head flowed [email protected] int. &[email protected] exh. pretty damb good for iron heads w/only minor intake bowl work... well the head cc.is 66.comp.ratio is 9.85:1 so to make a L.S.S. dyno #s 406 lbs.@5100 430hp @6200. but the heads leak what should i do.W/.040 gaskets comp.would be like 10.6:1 thats not pump gas friendly.