I rarely log...maybe 5-10 times a year...but really enjoy the rush now and then of going fast on a 9 foot board. Not interested in nose riding at all...lined up, semi hollow waist - chest high waves, slotted, high line kind of stuff. Since i wont longboard enough to really dial stuff in, i'm interested in how these fin setups might ride. So far the only one ive used is the single squirrel fin and find it really springs you off the bottom and shoots you down the line. board is HP 9' x 22 1/2" X 2 3/4" Setup one- 9" squrrel fin:Setup two- 3.25" side bites, 6.5" cutawaySetup three- 3.25" side bites, 7" takayama off an old single fin egg:
I have a fin similar to the squirrel fin on my 9-0 Bing Trimulux (single fin only) and it is the bee's knees for everything from mushy crap to solid chest + fun surf. Since you have a 2+1 you may also want to try 4.5" sidebites with a 4.5" trailer for a true thruster set-up. I have found large-wave nirvana with this setup on my 9-4 Soul Performance speed log. Nice hold on steep faces and great tight (for a longboard) turns. Of course when we get head to overhead surf, you will probably grab a shortboard and leave the log alone in the garage pining for you to return. . .
The 2+1 has really been a misused setup. Unfortunately, it's been a real magnet for guys that think that want the latest gadget or (never having a single fin) think that a single fin either can't turn or is for geezers. The truth is, with the right shape, 2+1s can enhance performance.
Personally, I think they require a "performance" longboard shape, with a narrower tail and some "V" for transition from rail to rail. I also think that (using it with the right shape) a 2+1 setup is ideal setup in steeper waves (OBX). While some may use 2+1s on a noserider, putting that setup on a wide, flat-tailed & soft railed board is a waste of money. Soft rails provide all the hold you need in steep waves and if you want to crank tight turns, the noserider just isn't the tool for the job.
All that being said, I think, of the three, that the squirrel fin is best for what you plan to do with it. The side bites will induce more drag than benefit for taking the high line and drawing a line down the face of a flatter (i.e. semi-hollow) wave. Personally, I'd put a Greenough 4A and lose the side bites for that. Just my 2 cents.
Oh...and to sorta echo what Mikey said, my 10' Cluster V has 5.5" sidebites and 3" trailer. On steep, juicy waves, that board can pull off some incredible stuff. Tiny tail, though, and good amount of "V".