There is always the risk that unintentional slack will form in the system during climbing, which will lead to a higher-force fall and the primary toothed-ascender damaging the rope. Why not just have the microcender as the primary piece? What is the downside of using a cam-loaded ascender for primary? I commonly use and am very comfortable with my back-up of clipping into a separate rope with knots. Therefore, the problem of having a microcender as primary and secondary belay, thus ruining safety redundancy, is not an issue here. thanks, I welcome any advice