Personally, I wouldn't go over losi 45 weight with yellows.
I run RC raven springs which are stiffer than the yellows and I believe I'm running 45 weight.
I ran yellows for the beginning of last season and they did ok. With anything more than 45 though, they wouldn't rebound very well or quick enough to adjust to rough terrain. I want to say I ended up using 45 with them. Even then, they didn't rebound real quick and the springs were generally stiff, so it bounced quite a bit on rough terrain.
With the RC Raven's and 45 weight, it did a lot better on the rebound and was softer on the first 1/2 of compression, so it handles the rough stuff much better. Since they are stiffer on the 2nd 1/2 of compression, they handle the big air better as well.