well, finally the long-awaited solution to the HP mystery has been solved
thanks to the outstanding work of the guys in this thread:
Impact on health of chipping skills (wizzszz, jimmyB, doer...), the HP calculation has been nailed down.
i've updated the chipping optimizer to reflect the new %'s (only the attributes were off), so now it should be much more accurate than before (with the same drawback of handling integer numbers only).