I'm not really sure if this will affect the gap or not, but there is a plastic set screw that goes in the hole underneath the buffer tube of the stock. Is it possible that you have screwed this in too far, pushing the 10/22 receiver up a little bit causing that gap?
FWIW, I wanted my 10/22 receiver to fit tightly into the Nordic stock, so I have my set screw fairly tight also...I have a slight gap, but it hasn't affected anything that I've noticed. My setup shoots well and it's very accurate.
Congrats on taking the plunge for a Nordic BTW...