I just wanted to take the time to thank you for your website as concerns your Multisystem fin concept. I have made sereral longboards the past two years and now ride them only as Quads. I have started to make some with the Quads only but for resale value, the multisystem is best. Its always instructive to ‘wire’ a board as a Quad and then try the center fin option to really understand the superior performance of the Quads.
As for rear fin positioning, I use an averaging formula between the ‘Guns’ and Longboards formulas but as the tail narrows, up go the rear fins to maintain looseness.
Again, many thanks!
Please see some pics attached of the fin positioning.