I've settled on 80/110 on 25mm conti gp4k and I'm 150lbs. I went as low as 60 and felt that I was begging for a pinch flat. 110 on both feels ok, but up front it makes things a little rough for me. Rear being hard feels much faster and my carbon post and saddle took out the difference in buzz.
You just have to do a bit of trial and error. Make sure to bring an extra tube and pump for when you get too low and pinch flat!