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On my race engine I have used stainless rings of 0.004″ thickness and recently rings cut from brass shim stock of 0.008″ thickness. It needs a head that is flat within about 0.003″ as otherwise it will not pull down on the ring evenly. I put a smear of silicone on both sides of the ring and a little more round the edges of the head to seal the water. I then put the pistons in the bores upside down without rings so the skirt will centralise the head on the block and the sealing rings in a position that is concentric with the bores. I then secure the head.
This is what I do but please consider that this will bring the head much closer to the piston at top dead centre as the thin ring is much thinner than a Scott head gasket and so there could be a danger of the piston hitting the head. When assembling a sports engine, we assemble first with an extendable two piece dummy rod so we can be sure how much clearance we have. You can not assume that because the engine turns over freely that all will be OK as the total assembly stretches approx 0.027” on an average long stroke 600 at about 4500 rpm. You need a static clearance of at least a minimum of 0.035” and better to be safe use 0.050”. Scotts give quite a large piston to head clearence, but there were quite a few variations according to the engine type. Unless you are going to do some careful checking prior to building, it is much safer to stay with a Scott gasket. It is always worth removing burrs and putting a straight edge or steel rule to check the flatness of the head first.