I would say that sail was set a little low, and is cut too large.
Gaff tops'ls are either kept aloft or set flying.
Kept aloft they're usually hooped to the topmast with halliard, down-haul, out-haul or sheet, a brail to get it back in, and tack line. There's sometimes a line that hauls the tack up, an up-haul, and two tack lines so the tack can be raised and passed over the gaff's peak halliards. These tops'l are furled in the cross-trees or top, since they're hooped it's not practical to bring them down every time you strike them.
Set flying means the sail is set from on deck and brought down. Many boats that do this had a jack yard, or a club on the luff or the head of the sail. My model of Pride below represents a typical jack yard tops'l which in the case of her type, extended the main mast above the height of the fore - it's normally a little shorter and she look a little like a ketch. Not the clew is significantly raise from the gaff. Only once do I recall us worrying about what side of the main the tops'l was set, and then we brought it down and reset it.
Later in her life, the jack yard was fixed aloft and a cable was run from it's head to the deck, a jackstay. The sail was hanked to this stay and set from on deck, the jack yard stayed aloft.
It wasn't like that during my time aboard, and I've never seen that arrangement on any other boat - see attached.
BTW: The gaff tops'l is supposed to be set on the windward side so it won't funnel wind down and back-wind the main.