Slender ass? I think not if it wouldn't fit.
Those advocating OCL have obviously never sat in a BOI, or senate estimates, or an AWB.
If you're wearing belt webbing (which won't fit) then you don't need to hit the ground running. If you do need to hit the ground running, you'll be wearing MCBAS, or the newer armour, and you'll fit in the seat.
The acft was acquired, in part, because it beat the Blackhawk in a DSTO-study modelling Amphibious force generation. The only acft that actually met the requirements of the study was Merlin.
If we followed the argument that 8 is all we need, and losing a section and a half would be awful, then we'd have bought Bell 412 and our Chinooks would only have nine seats in them - unless we're OCL, which apparently is tops, and we'd forget all our previous arguments and have 85 pax standing back to back.
No argument Black Hawk would have been easier to bring into service. MRH90 will end up giving better capability to the ADF.