G'day Capt
My experience is similar, life long short board surfer and lots of kiting experience. I'm a bit lighter at 80kg and my standard short board is 6'1 28l.
At the beginning of last summer I thought I'd have a crack at a sup and the fun factor has vastly exceeded my expectations.

Started with a fanatic allwave 8'9 145l used it for about 6 months and when I thought the board was holding me back (surfing) I upgraded to a Jimmy Lewis world wide 8'1 110l.
First time I took the jimmy out I figured I'd made a mistake as it was really hard to stay on it. Stuck with it and after about 5 or 6 sessions felt pretty stoked with the board.
The allwave was a great learner but felt like a boat on the waves.
The jimmy feels like a surfboard and goes unreal.
Really glad I didn't go too small at the start it would have been frustrating for sure.
Cheers