Hey Hate N'
Dennis is right, the little 2 3/8 turbo side bites are very loose. Principally, that "loose" feeling you are talking about is the fins FAILING. Very few fins are built to fail.
The smaller the area and/or depth, the easier it is to get the fins to fail. The only other fin in that size range is the SB2's that are 3.25".
Another thing that I have found will work is to increase the cant of the fins - it REALLY changes the ride though.
If you have a pair of fins that you don't mind wasting. Clamp the base in a vise and then with a heat gun heat along the base until it gets to the point where you can bend the fin. A mild increase is from 3 degrees to 6 degrees. Bend it to 12 for an exceptionally weird feeling.
Another option is to heat the entire fin up and then bend it over a piece of 4" diameter tubing. You'll be a Futures Vector 3/2/1 foil.
If you STILL want looser, you can always cut down an existing set of Futures fins. Make them any depth and length you want.
For the OTHER way, find a pair of Black Stixx and see what it's like to get increased drive.