i would say that the angle on those fins is so extreme that they will cause more drag than glide. i may be wrong but i wouldnt want to be the one spending all the time to find out otherwise when the modern bonzer versions work so well.
maybe those runners fell over when the glasser left the bay for the night and when he came back they had set at an extreme angle.
I took the first board I made and cut away the tail as a stinger added a 8" center fin and 2 side runners 3x9 set at 45 deg.1/8 toe in. The board goes like a rocket but seems to want to stay high verticle. its unfortunate that I didn’t think enough about where I was cutting for the stingers at. I get a bruise on my knee ever time i ride it.