I think there are probably better hikes with more lakes to see, but I drove up to Harts Pass one year and went in on the PCT to the West Fork Pasayten trail. Hiked up the WF to the Middle fork, out the Middle Fork Pasayten with a side trip to Buckskin Lake. Fishing at Buckskin was excellent for west slope cuts in the 12-18 inch range and it's a beautiful lake. No need for a tube or water craft. The lake is very deep and fishing from shore was very productive. Lot's of scuds in the lake but those fish weren't particular in the least. Scud patterns would be good but they hit anything that moved. But that's been my general experience with the westies, they never seem too particular. I also fished both forks of the Pasayten. All the basic attractors terrestrial patterns will work good for surface action. Smaller stimulators, humpys, royal wolf, caddis will get get takers for smaller fish in the 8-10 inch range.
The Pasayten is really spectacular. Wish it wasn't so far for me. Are you headed up this year? It's getting late but you would most likely have the place to yourself.