One reason for hot/cold differences for all iron engines is valve material. Many aftermarket valves are made of stainless steel, which has about 1.5 times greater expansion than steel.
I've got stainless steel valves in my poly - that was another reason why I went looser. I'd read .02" for the stainless.
And I am going to do what you outlined in post #12 - I'm going to doublecheck the cold right now, and then hopefully do the hot check tomorrow.