I was looking at buying a 16" pencil barreled upper for my M4 lower. Currently it has a nice M4 upper with Aimpoint, BUIS, m33 foreend, a tango down VFG, and a phantom. I would like to get a pencil upper w/ an Eotech for some lightweight action. I handled a pencil barreled colt in the gunshop the other day and really liked the weight reduction and change of balance. I think that getting this setup, a few more mags, some magpuls, a load bearing tac-vest, and an Isreali style sling would make for a sweet go-to gun package. So wadda you guys think? Pros & Cons of the pencil barrel?