for NeilMac, why dont you use a helical? A lot of guys over here in this area who shoot fingers, love helical with their fletching...
I'm only using field points (no hunting in the UK), so a straight or offset straight fletch will give me the fast stabilisation I need, and will also maintain as much speed (velocity) as possible over distance, as I am shooting 3D's out to 60 yards plus.
Dedicated Finger Shooter.
Shadowcat(s) with Barnsdale limbs: Davis The System, Free Flyte rest.