All I can say is that last year I shot 4 3" feathers and was able to get excellent broadhead flight, even with big snuffers. The main advantages are easy nocking of the arrow, and better cable clearance due to the lower profile of the smaller fletch. Control for what ever reason seemed to be better than with 3 4" feathers and very close to what you would get with 3 5" feathers. I can't explain it all, but I know it works. This year I will probably end up shooting 4 blazer vanes on carbon arrows.

you going to put them on offset or helical?

I put them on with a full right helical. Of course, with the feather only being 3" long, the right helical doesn't appear to be that extreme.

having 4 feathers woudln't work with a wb would it?

Why not? Might have to set them like an X on account of the newfangled stiff bristles on the bottom of the biskit but other than that I'd think it would work.

I fletch all my arrows with a right helical. It helps stabilize big broadheads better. I shoot a Whisker Biscuit rest so clearance is not much of an issue.

I use 4 2-1/5 feathers with a full right helical ( cant hardly see the helical) I get very good flight as my field points and broadheads have the same point of impact out to 35 yds which is where my Keller pendulum bottoms out. My protec is set on 50 lbs for hunting. (unable to pull heavier weight due to nerve damage in neck) GGBH