[MJN]

Zero deck height with steel rods and a 0.040" head gasket is about a close as I would go.

Machining 0.015" off the ring land part of the piston is not going to affect piston reliability much if any on a N/A motor. As the piston has a dish I would bet that you are not actually reducing the crown thickness at all. On the other hand if you price having the pistons machined at a reputable shop I bet you'll find that a new set of pistons doesn't look so expensive after all.

On the other hand machining the pistons is not a bad thing to do. I used to build 1430cc Mini Cooper S motors by taking Triumph 2.5PI pistons and machining more than 1/8" off the crown to make them work with Cooper S rods and an offset ground 1275 GT crank. Those suckers survived at 8000 rpm with no problems.