I have this mylar, square top mainsail, labelled only with the Hobie "H." Dimensions: luff- 25 ft, leech- 24.8 ft, foot- 8.3 ft and the square head- 2.4 ft. Thinking it is off a Hobie 17 or a Hobie Tiger but can't find exact specs to prove that. Any ideas would be greatly appreciated! I have photos but not sure how to add to this thread

It is too big for a 17 sail. My boom is 8'0"

The SCHRS data set would be a good place to look. https://schrs.com/ratings.html

According to that, the luff of the Tiger (VLM) is 9.05m (29.7 ft), so your sail probably isn't that.