just curious.. My carbon surfing paddle used to be too big for my body size and then a deal came up for a starboard bolt in tiki-tech.
The way smaller head size gave me a new lease of life on sup-surfing and that's all i've used for the past 8 months.
Does flex a bit, but easy to get speed from a standstill without too much force turning the board and tracks well.

Wondering whether I would get any added performance in actual sup-surfing if I went to a similar size paddle but a 'sup-surf' style head?

I tried my old one a while back and it ruined my surf, was horrible

This thread from a while back is interesting, particularly Deano's comments if you scroll down a bit.

www.seabreeze.com.au/forums/Stand-Up-Paddle/SUP/What-size-ke-nalu-paddle?page=1

Not sure if this is still the current thinking, but it seems to make sense to me (and my old shoulders).