I've got a 2000 or so Hardrock I want to convert to an 8 speed this weekend. The mechanic at the now closed LBS told me I could use up to a 9 speed cassette on the frame when showing me how to do wheel bearing service a few months ago after noticing 2 spacers on the axle. I've got a new Shimano 8 speed cassette (the current cassette is a Shimano 7 speed), 8 speed Shimano shifters and a 9 speed RD I've been using with the 7 speed cassette for years, as well as a new 7/8 speed Shimano chain. I'm assuming I've got the parts I need and then some; will I need to use both spacers to maintain the correct spacing after switching to the 8 speed cassette? Or do I remove only 1? Remove both?