I received a Tiagra 9sp. RD for next to nothing, will it work on a 7 speed Shimano HG freewheel with Shimano 7sp. SIS shifters. I would think that as long as the limit screws are adjusted correctly it would work with the range I need. I'm sure there are plenty of you guys out there who built a budget project and tried all kinds of combinations as the parts became available.