I'm putting together a 440 and would like to know how tight I can run piston to cyl head clearance. Currently I'm .031 in the hole and would like to up the compression. The rotator assembly has already been bought and balanced, so piston change/chamfering is not an option. Rule changes say I can run more compression than I current have (10.9). This motor (iron block, stock LY rods, NHRA legal CP pistons w/906 heads) will never see 6500rpm. Right now the piston-head clearance (w/.020 steel gasket) is .067. Can I knock .020 off the deck and still be safe? What is an acceptable clearance on a motor with negative deck height?