Whiteside I steep, I've not tried it but I would expect less than half of it to be rideable?
Which way off Grasmoor did you go, the only route down to Crummock I've done is via Wandope and Whiteless Pike, those are two briliant descents, but they can be very tricky if its windy as you get a gusty cross wind that makes it very difficult to pick your line.
Did you ride off via Lad Hows? Looks like that could have some potential, but ti's one of those that is difficult to justify, if you already know a cracking route off so I've never done it. You know what I mean, you spend an hour and a half slogging up Gasgale Gill and you don't want to risk the effort on something that might only be 50% rideable, so you go safe. Let me know what its like if you did it!