I have made my shims for years --I have used them on about 100 big block mopars and have never cracked a head because of shims--can it happen? Yes. Have I ever seen it ? NO and if you read Hughes website about preload--( and no matter what some think he knows) you can run anywhere between zero and two turns and more --if you want RPM out of a hyd cam use zero and put up with the noise--if you want them quiet--put 1 1/2 turns and its like a mouse peeing on a ball of cotton kinda quiet-You will be FINE with what you have unless you expect to turn it hard--like over 5500 hard. A .015 shim will not hurt one darn thing even if it is made out of a beer can IMO. PM me and I will send you a set for FREE ( not made from beer cans) and two will have the bigger hole to make you sleep better. Glad to help. One more thing the Cresent moon shaped shims ARE the best choice for thicker applications but not needed for a .015 or .030.