Dude has a 6700 setup.

None of those derailleurs were ever rated for more than a 28.

Having said that, doesn't mean you can't put on a 30 or a 32, you just don't know if the b-screw will allow enough adjustment on his *specific bike* to clear that biggest cog, in the small ring.

Good news is that you can put on a 9s mountain derailleur, with the correct spec for whatever, 30/32 you want to run and do it that way. Capacity will be in spec, max biggest cog will be in spec.