Last year I spent quite a while looking for the same info as you and came up with nowt. A mate and I started at the southern most point and went anti clockwise. We got off track almost immediately. The msrker posts are not obvious. The going was very much off piste and the route much better on a horse I reckon. Hours later we came across the first little info hut thingy, realised that we were getting nowwhere fast and exploited past motorcycle event knowledge and use a closed RUPP across the range to hit the tarmac at Dixies corner. More pioneering brought us to the start. I seem to think that our average speed was about walking pace. We were not making serious errors, it was just very slow going. We gad 1 CX bike and 1 MTb, neither were especially suited.
Good luck.