You can add me to the list of ladies suggesting you skip the long run. You've got enough time leading up to your 1/2 marathon that you can do that.

There was a time or two I had to drop my long run when training for my marathon to get in the bike training needed for the HIM. It actually turned out to be a good thing because my legs recovered faster from the cycling going into the next wk.

Best of luck on your 300k!! You will do great.