Damn man, I'm late to the party?
Yeah totally forgot there's a GBB and AEG side (metric/imperial).
Anyway, mine's pretty straight to me...but yes, there is a very small height step between the upper and the rail. Beyond that, it's still parallel to the upper though.
(yes it takes RS NSR panels)
Also in terms of realism - the keymod even has the scalloped profile on the backside as per RS Noveske spec. Not sure if it's immediately obvious in the photo below but the scalloping is very subtle.
For the record, I'm not affiliated with the store any longer but I do stand behind the product descriptions which I did write. :P
chaz, when you tightened the Torx bolts, did you do the bottom ones first, then left and right in alternating orders? This may make a difference. Similar to putting on wheel nuts in a cross pattern to ensure proper snugness and alignment, I would apply the same principle here.