To qualify for this Challenge Cache, either the sum or the product of the difficulty and terrain for every square of your difficulty/terrain grid, multiplied by the number of finds, should equal 25 or more.
For example, you have 2 finds at difficulty 3.5, terrain 4. (3.5 + 4) * 2 = 15 which does not qualify, but (3.5 * 4) * 2 = 28 which does.
Here is a table showing how many finds you need in each square:
There is an atrocious signal here. I averaged the waypoint for 10 minutes on my Oregon and cross referenced it with my iPhone, and I've given you the best hints that I can. Also suggest you take a torch, as it is dark under the rhododendrons.
More parking options listed on GC796QV VW - Stream