oh yes, as with most stuff in life, there is no "best feather length". however, there are less than smart feather cuts that don't belong on a trad hunting arrow and i do hope for the sake of this thread we don't go there ... please.
yes, you can do a full helical 5.25" feather fletch on a skinny beman ics 500 carbon shaft, that's what i use most ...
... the feathers are tape fletched, dotted with duco fore and aft and will not come off, even in a hog pass thru (4-fletch 4" offset banana feathers) ...
... or even after laying in the carolina woods for 3 years (4-fletch 4" offset banana feathers) ...