XTB tri-hull? No such critter that I know of, but the only XTB I'm aware of is a 21' which is not a tri-hull. Seems I remember them building a 15' tri-hull back in the day, but there was no XTB designation. XTB21's were built from 1985-1996.
Not sure where he came up with 17.5, but I know for fact they were made in both 17' and 18' versions. They look a little like a tri-hull from the front but are very much V bottoms.
Agree with 22R ,i always thought they were trihull , but have a friend who had one years ago and swears iy was 15ft. I always thought that boat was 17ft.
Like I said earlier, they did build a 15' bass boat back in the day, but I don't remember the hull designation. Don't think that was considered a tri-hull either, even though the bow was shaped the same.