RE: Draw Length Measurement
 

Over the year manufacturers have come up with all kinds of measurements for arrow length. From the string at full draw to the handle to the center of the button and the front edge of the riser. If you are shooting a cushion plunger, I would recommend a measurement to the front of the riser. If you shoot an overdraw, where the arrow will be behind the center hole I would suggest 1 1/2" from the front of the rest.

RE: Draw Length Measurement
 

http://www.huntersfriend.com/drawlength.htm

Probably just verifies what the above posting experts are telling you, but good photos.