What is the rule for-(longboard) bigger/smaller sidebites with bigger/smaller center fin? if I had bigger sides, and a smaller center…would the board be more snappy like a thruster? I noticed that the fins on my 2+1 are pushed up compared to my thruster. I am very confused… Ive seen longboards with twin fin sides and a small center. How would this work compared to a standard 2+1 setup?
I saw a killer King Fish (8’ plus longboard fish) at Rincoln last weekend. . Every design has its nitch. I’ve been hearing that alot of Hawaiian LBers have been useing small thruster side fins (X-1 or G-2000) side fins for side bites with a 6" cut away center fin and really getting alot of drive from them. I think it’s a matter of having enough power top drive that much fin area. If it’s micro stick to a single fin. If you’re out in some power, go for something closer to a thruster setup.
Smaller sides make rail to rail transition quicker. Conversly larger side fins slow rail to rail. This is a problem in hollow surf where quickness is more important and plus the sluggishness of a longboard can compound the problem. Mushy surf the larger side fins do add a bit of snap by giving a pivot point on the rail. Also they can add a bit of drive. The larger the back fin the more it pulls down and lifts the nose changing the balance of pitch aft. This provides better noseriding and better handling in hollow surf. In flat faced mush though your board may stall out and be be hard to get going especially around sections. My personal rule of thumb is larger sides and a smaller back fin for mush, a larger back fin and smaller sides for hollow days.
any good dimensions or #‘s to throw around? say for a 9’ longboard… how far from the tail? what about toe-in…1/4" 1/8"
9-2 long 13 1/2 tail, 22 3/16 wide 17 nose 2 15/16 thick Harbour Terry Simms Performance Model the back edge of the sidebites are 16 inches from the tip of the diamond tail. the back of the fin box is 9 inches from the tip of the tail. 
Finamon, how big are those side bites, and how big is that center fin? You give the board size but not the fin size or placement. TK
Everybody likes a little different feel. Personally On an 9’0" performance board I like a cutaway center about 8.5", I have a template that’s a favorite. It has enough rake and tip profile for nose riding. I think little cutaway rail fins about 3.25" - 3.75" are fine depending on the size of the rider. and the width of the board. The size ration turns out to be closer to 3 to 1 than it does 2 to 1. Some perfer a little flex - tip action. I prefer ridgid fins. If the whole fin toques a little cause it’s thinned down that ok. Mahalo, Rich
sides are the DT o’fishl, and center is 6.5 harbour like in the pic
I think you mean DS O’fish they don’t have a DT template. Those are 4". W with the fins set up the way you have them you have alot of quickness but not big wave drive. You can move the center back on bigger days and surf this set-up off the tail and it’ll hold in fine because the tail of your board is pretty narrow. If you want it to have more of a longboard feel and nose ride. Try either RR or SS side fins and O’fish’s 8.25" cutaway like I mentioned before. My template is similare in many ways to theirs. A second choice for the center fin would be a their fast carving 8.25" but that will stiffin board action a little. Mahalo, Rich
thank you Rich. How would this board ride as a single, and what style/size would I want to use?
oops, the sidebites it came with were “TT” I have a set of “ss” and “ds” as well. 
Hey F–. I would think you’d need a flex-tip if you’re going to surf this one single. The tails pretty narrow so you’ll need to be able to work off the rails some to turn it with on fin. If you put the fin back it’ll be pretty stiff I think. An 8.5" TK flex would be a good choice I think I’ll probably nose ride pretty well with it too. http://www.rainbowfins.com/surf_fins.htm This board would be fun to surf with big cutaway rail fins and a little central stabilizer too. You could really go rail to tail with this kind of a set=up. Mahalo, Rich