some of the old New Guinea strips tested the limits.
Civil certification didn't address STOL .. which was a specific MIL application.
In the olden days when Australia oversaw PNG's aviation, there were particular ANOs which addressed the reality of developmental aviation for PNG and these contained numerous deviations from mainstream rules.
I can't remember the details at this distance in years but I suggest that the bulk of deviations were addressed via operational concessions, either across the board or by operator.
Certainly the Nomad could get on and off the ground in a stylish fashion and Stu played it like a puppeteer - my first exposure (as ballast) was on some performance T/O and landing trials with Stu and Pat and, in the absence of any briefing to the subject, I had my young eyes opened as to its capability.