dirtydozen

Hello,

I would like to replace my bent rear derailleur.
I bought my bike second hand from a bike shop, groupset is 105 5700.
I have a triple chainring (50/39/30) and a wide cassette (11-34).
Looking online it says it won't work with a cassette that goes above 28T or 30T with the long cage.
They also talk about a total capacity of 37T, which leaves me with 17T capacity on the rear, which is 11-28 and nothing more.

I mean surely i can't go wrong replacing the RD with the same model (right?), but on every website I go it says the RD is not compatible with my set up basically.
I've seen a comment from a guy that said he made it work with a 11-36.

Any ideas how to proceed ?