my one and only stay at a HSC was at May Lake HSC in 1996
if you have time, be sure to pop up to the top of Mt Hoffman from there. Nice view looking over at Clouds Rest and Half Dome. Mt Hoffman overlooks the lake, but you go around the side on easy terrain and trail. The very last bit on rock up to the radio tower is optional. I'm thinking maybe it was 4 hr round trip from the camp to top and back. 1600 ft climb.
Mt Hoffman we 4 snuck in when someone cancelled. Even so, the 8-person tent cabin only had 1 other person. Did not stay to use the propane-powered hot water showers, but I guess they still have those.