I checked and actually R1.1 and Excellight would be just 1mm off one another.
This should be feasable.
Depends if the new one calls for 1mm longer or shorter. If the original rim was built with moderate tension, but the newer rim is 1mm larger ERD, I would attempt to rebuild with increased spoke tension and I suspect it'd break even.
I round up or down 1mm in spoke length depending on inventory. For double walled rims it's not the end of the world if threads go past the slots of the nipples, unless it means you've bottomed out the threads before reaching the appropriate tension.