Yo, i have just had my Stingray hh de-fretted and 40-95 cobalt flat wounds put on it, so far i'm not too impressed. The sound is fine but the feel of these strings is very sticky. I'm hoping that this is just because they are brand new and need a little wearing in. I know that i chose light gauge but these do have a very ropey-tinny quality to them.
I have 40-95 ernie ball round wounds on my fretted which i love and am used to, also i have 40-95 flat wounds (not cobalt) on another fretless which are also fine which leads me to believe that the whole clangy sticky feel is because they are cobalt.
I'll probably write on here again in couple of days insisting that they are great, switching strings is going to feel strange at first.