whats wrong with what your shooting NOW?

With vanes, your FOC is approx 10.1

With Feathers it is 12.5

So it depends what you want to use.. Both are good.. Vanes are a little Heavier but hold up better in inclement weather..

I personally like feathers better, because they stabilize your arrow better due to increased drag, especially when shoot a broadhead..

as to 4 inch or 5 inch.. the little bigger will give you more drag and more weight.

What kind of rest? If you shoot a drop away, I would suggest staying with the Helical.. thats what i shoot.. Better stablization with helicals.. If you shoot alot of 50+ yard shots, then straight vanes will drop less at those distances..

So up to you i guess...
SHOOT BOTH AND SEE WHAT SHOOTS BEST

MY TWO CENTS