Iīm not sure how the N/R-Basic engines are designed, but if there is a rough anodized surface on the cooling head where it meets the head button you could sand it smooth and flat to help-out with cooling.
Sometimes a little thermal compound for computers can get the job done also, but thatīs sort of a last resort.
Then regarding if "two slices of aluminium" can make that much difference, I bet there is a difference in the diameter also... (and I get it to 1 slice of aluminium...
)