Lower gearing is great on hills, technical rocks, and in real tight stuff, but for bikes with a big midrange burst like the 300, it can make the bike more of a handful in the slick stuff, as it comes on the pipe faster in each gear. I tried 13/52 on my 300 EXC in a slick muddy HS, and fought for traction the whole time. You'll find you have to ride another gear higher to keep it from breaking loose. On my GG, I have a selection of rears and two different length chains, which I swap depending on conditions.