3. Will the same barrel ever be offered in 20" length?
That is the DCM Barrel that they sell. You can order it alone or have them build it into just about any configuration you want! I will add that it is a very accurate barrel too as I had one that I competed with for several years!
4.Would you consider building a flat top upper with folding front and rear sights...a 16" super-light wt. barrel or M4 barrel...
I know they will do the above...
... with a mid length gas tube and graphite handguards with
optional rails with at least one in the 11 oclock position
Why mid length system? I leave the rest to someone else but I really don't understand the pupose of the mid-length grips. Does this system place the bayonet lug far enough forward to allow a bayonet to correctly mount on a 16-inch barrel? Now, that I would get excited about!