Can’t read the size of the center fin but I’d say in small waves you could go smaller. Wouldn’t hurt to try one an inch to an inch and a half smaller and try moving it around some. I know it’s difficult to catch a bunch of consecutive days with comparable good waves to really check but it couldn’t hurt? Fast closed out waves aren’t necessarily the best proving grounds. Give it a try in some good waves and have an extra center fin to play with.
You are right , its not one board fits all , some folks have difficulty with different board designs , I know several guys that cannot seem to come to grips with cambell bros boards while others would ride nothing else . good luck.
I found that they work best with your back foot over the fin.
If you haven’t surfed on a single fin before it will be extremely different than a thruster or twin.
Try placing your back foot over the space between the center fin and the rear bonzer fins for turns.
My initial response when viewing photo is too much fin to far back. The Bonzers we made worked best with smaller center fins moved up so the “runners” were in the middle of the base of center fin. Try a smaller less rakey fin. Bonzers are quirky to fin placement. I designed a weird “Blackjack” fin that really changed how they rode. Added a corner to the turns that the boards were lacking. Don’t give up so easy play around figure it out. Thats half the fun.