Does anyone know if the 11-27 and 11-28...
Does anyone know if the 11-27 and 11-28 are compatible with the SRAM Red rear derailleur?
The best answer you will get on this is "Probably" and until you see it don't believe it.
In reality they are several technical changes to the 7900 series so if you are running SRAM Red why wouldn't you just get the OG-1090 cassette in 11/28 size? It is just as light, lasts for more miles, and is cheaper than the CS-7900 cassette.