I keep some Cajuns dwarf crays with bolivian rams and have not had any problems. The cray comes out and eats nearby the rams.I know shrimp shouldn't be kept with German Blue Ram's but what about dwarf crays?
I'm planning to take down my 40g and redo the entire tank. My plan is to keep the guppies, Clown Pleco, and male GBR (possible female if I can find him a suitable mate). With a 40g you'd think there would be lots of room for them to hide if the GBR does get a bit aggressive.
You can try it and see if it works. Remember to provide the cray for a place to hide when it molts.