You SHOULD be able to pull the mast all the way up, keep a slight amount of tension on the halyard (enough to just keep the sail from sliding back down), rotate the mast, and with the mast rotated and someone maintaining that slight tension on the halyard, pull down on the sail - you shouldn't need downhaul to pull it down. Remember that when you pull down, the mast must still be rotated sharply and it will probably help to have someone keeping a little bit of tension on the halyard. Sometimes, however, these things defy all logic and maybe NOT putting tension on the halyard will let it come loose. Sometimes rotating the mast in the other direction will make it come off easier...point is, use these instructions as a guide but mix it up until you find the combination of sequences that will unhook it - you'll get it.