As for the weight question yes it does add a fair amount if weight. If I can't find a 8" barrel I am going to keep the fake silencer off and getting a 1/2 X 28 AR-15 flash hider to fill out the barrel. The barrel is pretty thin and it moves around alot easier without the fake suppressor on. I have not compared the accuracy to the 8" vs 16" but I am only using it for 50 yards which is why I wanted the smaller barrel, but I can't complain with free krinker kits.
FWIW I just put my kit on this evening and its so sweet, I am stoked to get out to the range.