For the OP. I have several bikes set up with Shimano 9spd RD's on a 7spd cassette and one with a 8spd RD on a 7spd. All work great. As for shifters, if you have a 7spd cassette, you need 7spd index shifters. Or a friction setup. Of course then again the OP doesn't know my skill level, so take for what it's worth.