What JesseT is correct - on a properly engineered engine, you will have a suitable squish area which requires the pistons to sit proud of the block deck by a blueprinted amount.. However you can't really do that with the LET pistons as the main reason they're used for turbo zetecs is because they sit so far down the hole its the only way they give you the reduction in compression ratio.. It's not ideal and it's crude, but it works!