"...it's not an AR." (heard that one alot before)
BUT, what it
is is a proven platform with a reliable operating system that fires an effective 5.45x39mm cartridge. what's wrong with the guy making it user-friendly then?
the Krebs appears to be tank-like in build, and with that much aluminum, will draw agoodly deal of heat from the barrel. the upper rail doesnt mount on the gas tube, but would still have to be removed in order to remove the gas tube, so rezero capability would be hampered.
http://www.krebscustom.com/MainPhoto-800.jpgthe veriforce rail you mentioned even looks to have a forward cant in the imges on their own website......
the TDI polymer has only one position to mount accessories at 3, 9 o'clock, so you are limited in your placement of grips, etc. and perhaps your shooting comfort.
TDI also makes a 5 rail aluminum system.
http://www.tdi-arms.com/images/large.php?id=250&num=2IMO, the best set-up would be a tri-rail forearm, such as the Krebs, coupled with a receiver-side-mounted optic, like a Kobra. that way, you can strip the weapon, even the gas tube to clean, without removing the optic. your irons will still be useful as back-ups