I completed a windy, hilly 300K on May 8th in 18 hours. I can't participate in the 400K, but plan to do the 600K on July 10th. No real problems on the 300, just tired and general soreness and what I think is an ankle tendonitis. How do I prepare for the 600? I've been working on speed on my midweek (hilly 20mi) ride and plan to do at least 100mi ride on each weekend. Do I need to try and complete a 400? Should I do 150miles, sleep 6 hours then do another 150?