Originally Posted by Kontact

There's no real reason you couldn't shift 11 with that derailleur. The total width of 11 is only 3mm more than 8 speed.

I'm using an old friction Mavic RD with 8. The one issue I range into was that the inner cage plate got very close to the spokes, so I put a 1mm spacer under the cassette.

I'm not saying it will or won't work with any particular set up, I'm saying that the actual width difference between different 130mm hub formats is very small.