I always cut at least one 30 rder to 20 rds. The 30 sticks out too far for practical field use, but it's nice for practice. It gets in the way of going prone,using bipod, doing "quick sling rolls", etc.
You'll DEFINETLY love the luminous sights, ambi safety, trigger job. As big as you are, you'll like a butt extention, and you'll be faster, from low ready, with a rearward extention of the pistol grip. I've always just used Bondo Car body putty, and wrapped it with black cloth tape, but Pachmahr or somedbody sells a larger pistol grip made out of rubber (or so I've read)
With the gun a bit shorter than "fitting' (butt in crook of elbow, first pad of finger falling natuarlly across the face of the trigger, gun handles faster. Need a TIMER to be able to notice all these little "twitches" of improvement, John. A NON-wobbly fit of upper to lower, handguard and stock ALSO help speed of aimed- hits, and so does a properly-made cheekpc. The latter should have two depressions. One on its side, for your cheekbone and the iron sights, one on top, for your chin and the scope.