brucelanthier has pretty much summed up what you want to do. Arrow length is a tuning factor. Doing what the typical person does - cut as short as they dare shoot with a broadhead - you eliminate the opportunity to use arrow length to fine tune the spine, FOC or total arrow weight of your arrows. Without using arrow length adjustments, you make it much more difficult to get that perfect flying broadhead.

My drawlength is a bit under 29" and although I have shot a few arrows in the 28" range, but most end up between 30" and 32" in length, depending on what I needed to get the spine exactly where I wanted it.