I'm glad to see a working HAMP write-up back on NH. Now with more fluff! I've never seen one of these used at an actual war; how does it perform as a primary?
I don't ever really get the chance to play with stock blasters, but methinks I would wind up using Elite/Koosh/Voberry darts since I'm big on clipped blasters.
For NIC wars, I've been using #8 slugs with McMaster-Carr foam since 2010. They're mega cheap and mega easy to make (both valuable since I tend to provide darts for large groups), plus they're pretty safe when made well (also valuable since I tend to initiate a lot of new players).
Optimal dart length is mostly a function of preference and barrel length/material. Generally, longer darts fly more accurately, while shorter darts fly farther. Most people use darts of 1.25" or 1.5" as a balance point.