If you're using the plastic flex fins that came with the board, I suggest you ditch them altogether and invest in a proper quad set. I had the 9'10" Hokua and rode it with the Shapers Asher Pacey set and a nubster fin in the centre. Also look at the Shapers Jackson Close set. You wouldn't want to go any bigger than the Jacksons. With a good quad set in your board you'll find it goes much faster, bottom turns should feel more aggressive and you'll get more release off the top and be able to slide the tail out.
I had a 9' Hokua which I rode a lot as a quad. I found the main difference between quad and tri fins was that I preferred the quad in bigger punchy beach breaks as quad held the rail better on steep faces and fanging down the line. The tri fins work nice in slower softer waves where you could link more turns together by doing a proper bottom turn and come off the bottom and hook into a top turn. I have ridden the 9'5 Hokua and it has a flatter rocker so a quad set up would probably give the board a bit more speed down the line and squirt out of turns. Quad fin selection is quite important though.
I owned a hokua 9.0 as well and really liked it with the PC7 fins. Tried the SA, but found them making the board a bit too dull.Same experiences as Steve...Quad in bigger waves and more for speed, tri (PC7 frontfins combined with a 14cm windsurf fin) in slower waves.
I used the smaller stock Naish fins in the back and a pair of 14cm K4 Ezzy asymmetrics in the front. The K4 front fins are quite soft so can go a biit bigger. I am also using Shapers Quad-E in my 8'5 Fanatic Prowave with a numbster which is a bit of an experiement. Have a similar quad + nubster set up on my 7'4 Deep Minion.