My Grayling can do a 5.5" banana with some minor tweaking, are you sure you're having issues with it? 4" are no problems at all!
The Bitz is a nice jig, but for what I paid for the Grayling (and a few extra clamps) I've more than gotten my monies worth out of it.
My next jig will be an Arizona EZ Fletch. True the standard is straight/offset only no helical, but I've not run into issues with offset feathers with my broadheads. The fact that I can get 3 feathers on a shaft NOW instead of gluing one, waiting, rotating, repeat, is awesome. I don't mind fletching arrows, but there's a lot more I'd love to do with my time than babysit a shaft.
I do love the look of a 4deg helical, though - it's a pain to glue on to skinny shafts. Looks like a prop from the back!
Glues I've gone all over, and still come back to Gel Superglue. It's not perfect, I've had a few feathers peel off (and some vanes that weren't prepped right really came off quick) but it's cheap and local and works for me.