I thickened the D fin on my new pig to about 7/8" thick, with the thick point well forward as you suggested.
I took it out again, this time at PV Cove, steep angle south swell, a tough angle for the Cove to pull in, but still 1-3' with 4' sets, the sets tending to close out, so you have to be choosey, but with a nice south wind texture on it (south wind it side shore there.)
The pig went really positive with the thick foil on the fin, definitely easier to turn and less stiff. Cutback no problem. I feel the big D fin acts like a big sale which really makes the board go.
On some of the bigger sets the board was just flying! On one wave I proned one long whitewater section and the board just pulled itself along all the way into the green. It definitely goes.
I rode only one wave frontside and that's when the board started feeling stiff again. Maybe the D fin works backside much better as you can push the fin more and put more pressure on it? But then again a lot of people seem to ride D fins frontside with no problem...