I have driven much of Highway 6, but never flown in the area. Much fun in searching though, found lots of my sort of airstrip.
There are heaps of airstrips all through that part of NZ. However, most of them aren't used as much as they used to be, because helicopters have taken over most aerial tasks. Do you know that South Westland has the highest concentration of helicopters per capita in the world, and by a huge margin? Where folks in other areas drive around in motor vehicles, people in that part of the world use helicopters for everyday transport. Parking up next to the school at Hannah's Clearing (half-way between Haast and Jackson Bay) early in the morning on a school day is a revelation as helicopter after helicopter lands to drop the kids off at school, then at the end of the school day, the helicopters come back to pick up the kids. A lot of those people live days walk beyond the road end in the Cascade Valley, so a helicopter is the only means of practical transport.
Anyway, I'm heading off now, travelling over to Wellington, then crossing Cook Strait to Marlborough early this evening....heading for Classic Fighters 2015 airshow over the next three days. I'll be online from time to time though, so I'll keep an eye on this thread.