I got the rail for the Carbine.
You can see where the mount clamps, it’s forward – you’re supposed to leave a gap fore and aft so it doesn’t bind on the barrel-band or on the receiver.
The clamping system is a lot like the hand-guards that clamps to the handlebar of my KTM off-road bike.
UPDATE:
The rail installed pretty good.
I used the steel-ruler to check and insure it wasn’t touching at either end by using it as a shim, and then to insure it was evenly rotated side-to-side with the same gap between the wood. While tightening the four screws it was necessary to maintain the same relative gaps-to-metal. A feeler-gauge might have helped.
I took it in and out of the stock several times checking clearances also before a final tightening. 
Looks ok to me…Gotta figure out what-height rings work. Regarding ring-height, in an email reply the Ultimak guy said, “When mounting to the Carbine, the motto is ALAP (As Low As Possible).” So far I’m happily impressed with their customer service.
