fin question

[Gilligan]

a while back i replaced the center fin with a smaller one to make the board looser. And now it feels like the board is definitely looser but has almost no drive in turning.

My question is would smaller side fins and a larger center fin fix this?
My board is a 6'7" shortboard shape tri-fin

[powndnstein]

If you put your side thruster fins back in it will fix it, but you don't need a big center fin just one that is a little deeper than the side ones. If you just want a single fin get a deep one with flex and that will solve your problem. A board that is a thruster usually has a much wider tail than a single fin board so it will always ride a little squirrelier than a board designed for a single fin which will have a narrower tail and by that you measure the width of the board 12 inches up from the tail and then the tail itself and these are the dimensions the shaper uses to describe the tail width.