RE: measuring arrow length
The correct length for you arrows on a modern bow is one inch in front of the point the arrow contacts the rest. However this is assuming your rest is set up properly, being directly above your grip. Basically the same spot you would measure brace height or true draw from. Probably pretty close to where your mounting hole for your rest is.
Some people like to shoot longer arrows when hunting that stick out beyond the riser for safety reasons. They don't like the idea of the broad head being directly over thier hands.
The WB is somewhat of an overdraw rest so your correct arrow length should not get you any where near the actual rest. Can you go shorter, of course you can as long as you get the properly spined arrows. Be careful about going to short, like less than one inch infront of the rest like you want to do. It is possible you could overdraw the bow and the arrow would drop out of the back of the rest and would land on your hand. This would suck with a fixed blade and be even worse if you accidently let the bow down while the arrow was there. Not a huge problem with the newer bows having very solid back walls, but it can still be done, especially with very agressive cams and high let offs. If you draw so much weight that you can't smoothly draw the bow thru it's whole cycle you could end up doing this when it drops into the let off part of the cycle. I see it quite a bit.
I would try and keep the tip of your arrow somewhere over the center of your arrow shelf just for safety.
Good luck,
Paul