I used that RDER & shifters from 12-28 7 speed, through 8 speed to a 12-23 9 speed on my 86 Rockhopper.
Although I had no need for an 11T small cog, I sincerely feel it wouldn't have been a problem.

Shifting actually got better as I added cogs, due to ergonomics of my thumb etc.
I probably hit my gear 95% of the time until I got N+1 with trigger shifters.
My friction shifting skills went down the tube.....