ORIGINAL: Grandviewer
On the Mathews forum there is a thread that measures the speed drop when using a WB. If I remember the diameter of the shaft compared to the opening of the WB has something to do with the speed drop. Tighter the slower the arrow but the biggest difference was 5 fps slower using the WB.
with the proper arrow and WB you should have a fingernail of light on the top then narrowing off to the 9 and 3 O clock position.
and yes you can have too much and too little this is on of the biggest tuning problems people have nxt to not having the vains set right witch should be 12-4-8 oclock ruffly....I shoot ICS 340's and never have had a problem........