Has any one ever done Merfins road which is on the right just after the second (I think) bridge coming from Ikamatua on the Blackball road). Its narrow but sealed for a few ks then shingle then farm track then bush.
Went up there on the weekend and stopped at a slip, there was a track round it but we weren't set to go on so walked it in the slush and light drizzle, goes on for ages and would be very hardcore but a real adventure (mainly gorse, scrub, slush, moss etc.) The track has been driven some time in the not too distant past, but the further we went the less use, until we came across a tree across it almost 1m in diameter. At one point it branches off and at the intersection there is a slump in the ground that you can hear water in and it doesn't sound like any wee hole under ground, perhaps a mine.
Permission may be needed to go on up, but would be interested if any one has been up that way.
The map shows it is a side track off a loop, but the rest of the loop has a locked gate.