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You can get up to and through diamond sands in BM without having any more impact than your average SM diver in Jug with proper tank selection and technique. Does that mean it should be done regularly? No. But it is possible. Some of the original exploration was done in backmount.
@Manatee Diver there is a negligible difference in al72's and al80's. That is an equipment solution to a skills problem. You probably also have sloppy stage rigging. Remember that the standard DIR style rigging is designed for use with a DPV, not necessarily with kicking. You may just need to continue to evaluate the rigging that you're using. Do you have a picture?