I've used the feeler gauge method with good results, although it can be a pain to gentley grind the OD to match the drum diameter. As you state, your drum tightens just past where it needs to be, lay the drum on a steel surface (removed from the bbl. of course)and peen the edges with a hammer as you rotate the drum. You'll be suprised how little peening it takes. I then lightly coat the threads w/epoxy and torque it down to its correct position(after test fitting). The epoxy is not for strenth but to lock the drum in place and seal the threads form moisture. It can always be removed if necesary, by applying a little heat to soften the epoxy...There is no fix for bad threads except to make them right before you proceed!! Thats a different subject altogether. :v
