Just looked at their switchblock uppers - the 10.5" would be pretty sweet. Hard to believe the rail is actually 9.5" as it ends right on top of the suppressor mount.
The 12.5" one would be a great host for the SPR/M4 can though, it’d fit very nicely. Both great choices in my opinion.
I’m going with the 10.5" switchblocked Noveske barrel as well and I don’t think that a 9.5" rail will work with the switchblock because of the carbine length gas system, unless of course you are cutting an access hole in the rail. Just a heads up, but let me know if Noveske has told you something different.