I own other knee warmers and I use them a lot including other castelli's. I know the tricks of keeping them in place. After two sets of these in two different sizes
(after conversations with you) these just will not stay up- I suspect it's the lining as I don't have this problem with other brands or sizing.
I've completed only one day with these and I'm glad I got them. It was a few degrees under Castelli's recommended 54 degree minimum and my legs felt fine (there wasn't much wind though). They seem a bit warmer than other pairs I have. They gripped pretty well, although I did have to pull them up once during the 3-mile ride. The soft material and flat seams make them very comfy.
Use on cooler mornings. Even though they fit tight, leg movement cause them to work down below knee. so after two uses, they went into the rag bag.