Well Wyo got MDS to work on his last year above 10K ft. Because he got his secondary machined. Sheaves were machined to match belt angle better, but it cost him a pretty penny ($250 or so). Before that those weights would not hold rpm. He tried everything too and was wrenching on the mtn like every single day. I kept telling him to give up and put Cat weights back in since day 1. But at least they worked after the secondary got machined. I tried them in my 2010 M8 years ago and could never get them to hold rpm even with no weight in them. At 11K+ ft it gets really bad. I stick with OEM cat weights. You will be fine though at your elevation w/ MDS.