Are 3" parabolic feathers enough?

[AKMAN]

Anybody using 3" parabolic feathers to stabilize fast (-ish) mechanical broadheads?
I want to feather-fletch some 330 spine Easton Hexx shafts for use in my new-to-me Chill R. (Should be here tomorrow...)
I'd put them on with an AZ Easy Fletch. (long version)
Plan is to use them for the range and a little bit of 3D stuff, but may try using them on sheep this year if I can get them to fly nice. Arrow would look something like 27.5", 75 brass insert, 100-125 mechanical/field point, regular nock.

Will a 3" stabilize this or do I need to go longer?

 

[Beendare]

Those work... BH tune for best results

 

[WoodBow]

I don't know what you call fast, but i am shooting around 450 grains at 296 fps with 3 3" vanes with no issues.

 

[OR Archer]

If you're hunting with them be sure to put some sort of waterproofing on them. If they get wet they're not going to steer the arrow all that well.