That's a really cool set up. I guess the carbine is the same action, just a different length barrel. I know you were worried about fitment...looks like everything worked out ok.
I had a cheap, low power scope on mine and bought a Nikon 3x9 from volsgo1 and swapped them. If you get a chance, try a decent scope on it, you'll be suprised at the accuracy of those rifles. You should be able to swap back and forth with that rail system on that stock.
Cool set up. My wife has pretty much claimed mine when she started "pinging" our steel target.