I'm thinking about some birkenstock insoles but, in the meantime, I think I solved the problem. I've been riding toe-d out slightly as that is how I walk. I read something about riding neutral or toe-d in so I tried it - just slightly toe-d in for a few days. Pain in the foot is gone as it shifts the weight more to the center and....it solved the problem with tenderness on the medial side of my knee on the same leg. Hoping it lasts, fingers crossed. But still, I might get those cork insoles to replace my Sol ones.