I think Rival comes in either short-cage or medium. Short cage can handle 28T cog and 30T chain-wrap, whilst medium can handle 32T cog and 37T chain-wrap. Your suggested set-up (with 50-34 compact chainset) would have 33T chain-wrap so you need to have the medium cage according to specs. So if the grades are truly ridiculous you could even run an 11-32.