A shooting bud of mine just got a K-80, the unsingle is the high pro-rib, he started shooting it and is doing very well with it; however, the comb is bottomed out Now the ? His double barrel has a standard rib--I believe it can't work as a doubles gun--with no downward adj.
There's 3/16th's difference in the height of the rib in the back. Should work fine. Pro rib is 3/16th's higher. If he's shooting over the target with the o/ u's, raise rib to achieve desired POI. I have the PR unsingle myself Hope this helps