The X-Harness is a great product! I was able to attach it to my MAV with no problems, and without even needing to look at the instructions (Which do not come with the X-Harness, but can be found at Tac-Tailor's website).
I carry a lot of weight on my MAV, and also attach my M4 to my X-Harness with a carabiner, and I have had no major issues with weight distribution.
The only downside is that the straps sometimes get pushed in close to my neck when I wear my aid-bag, but that doesn't happen too often.
It really works
Thiswas one of the best things that i ordered from uscalvary and i have never been happier, thinking about getting it but having doubts, forget about them, and get the vest.(Great for hunting).