ProComp/Speedmaster aluminum heads

My cam card says .022 lash... I usually set it at .019 cold and let it rip...
For some reason I'm thinking aluminum heads required more lash when cold??..
I looked it up and I guess add .002 for cast iron and subtract .006 for aluminum..
Best I think I can remember Ken must have told me to set at or around .016-.017 hot...