What size of ski - is this the 67.5??

Here are some computer generated numbers for your weight, using pretty slow water (125 uS) and 80 DegF.    

31.00"   7.003  2.492    0.895 - wing 6 to 8, no more.

Hard to tell without video and conditions info, but these should put more ski in the water, but at the same time shorten your turn radius, get you wider before the ball and keep you moving through the turn better.

The planing angle of a ski is controlled by your boot position on the ski. A light skier on a large ski will plane with insufficient contact under the front boot =  tip high. To correct this, the boots go forward along with the fin to maintain the required slip in the ski, that's why the DFT # is higher. Basically you are climbing ahead on the ski, and putting more ski behind you for support and cross course speed generation.

The fin setting is to improve the performance of the ski as it rolls onto edge, putting more ski into the water before the ball, and allow for a faster turn as well. If the boots forward setting is necessary, then this fin setting is used for the same reasons.