RE: Distance between nock and fletch???
Fletching placement is best when tailored to the individual shooter.
So that you can obtain the rearmost position of your fletch, which (rearmost) allow as much room as possible for the shaft to begin to stabilize before the feathers/vanes meet the rest, and to provide finger room if finger shooter, and to keep the fletch/vane from pushing against your face when using fingers or release, measure for installation of the fletch from the tip of the actual nock you will be using, not from the back of the nock bushing.
If you measure from the nock bushing, depending on nock length, you could end up with fletch too far forward or too far rear once you install your nock..
Average distance from nock to where the rear of the fletch/vane is, is usually "1 to 1-1/2". Take your measurement and then eye the space and determine what distance your believe you will need.