That their koopun was on the ruff where the rain warshed-ed-ed it down orff.
I say both. I don’t say “koo-pun” or “koop’n” but know people that do. I was raised with “KOOP on” but I knew people who said “QUE-pon” but if the said “QUE-pon” they tended to hyper-correct a lot of words poorly and usually had crunchy bottle blond hair and too much makeup.
Central New Jersey, USA. The higher the area’s income bracket, the more likely they said “kew-pon”.