Draw length, I notice that this hot potato is one few want to touch, Well here goes. Most archers are over drawn! This is a fact. The guideline of the V of the string is not as great as once indicated either, it depends too much on your anchor point (low anchor point lengthens the V) and on the A2A of the bow (short A2A seems to over emphasize the V). The only really good way to find out what is best is to get a good coach or go to a class with GRIV, Bernie, etc., and have them help you. Personally, I have tried going up and down and found that it changes with the release I am using.
Try this little game to see if you are close. Stand against a wall, straight and tall, and spread your arms to the side, straight out. Now have someone mark the extent of your fingertips. Measure the distance and divide by 2.5. This is close to what you should be shooting (close only). When I do it, I get a calculated draw length of 28.4" but I shoot very comfortably at 29" using a Stan Sierra II BT release. With my form, I am solid on target with this setting, but if I had a longer D-loop or a different release this might/would change. Many pros claim that a mere 1/8" difference in draw length makes all the difference in the world to them.
Kisser buttons, use dental floss tied into a knot, or use serving material, and you will loose little to no speed. More important is accuracy. Loosing ~5 fps in speed but gaining accuracy is not a bad price to pay.