In reply to Coel Hellier:
Yes. This is from the wild country instruction manual for my ziplock harness:
WARNING: To ensure that there is no
slippage of the webbing whilst
climbing the Ziplock buckles should
be synched tight and the “webbing
tail” (minimum tape overlap of 10cm)
remaining should be secured with the
elastic keepers provided (see
information labels on the harness).