I have a number of different PA28 Check Lists, all of which were derived from the FM. Each contains a CRASH/EFATO Check varying from 8 to 10 items. The PA28 140/180 slab wing Check says Door UNLATCH and on the PA28-161 taperwing, it says Door -Top Handle UNLATCH.
Personally, I would totally unlatch the door as any distortion may prevent it opening.