Running a tap through risked ripping the nuts out of captivity, wasnt happy with that thought. In the end I took the oversize(on dia) BSF bolts and shaved them down in the lathe until they fitted. Did one spoiler with 2 bolts, OK. shaved 2 more bolts, packed it in for the night, couldnt find them today. Scrounged a couple of bolts that fitted...sort of, fitted the other spoiler. Pics to follow......Have emailed Classeparts about the thread....
Not good with spray cans, so the finish is only fair...Should do its intended job if ever I can get it up the necessary speeds.