I made my 40K with no problems from my legs and no stops. I was planning on taking a break half way for a snack, but decided to just keep going because I felt so good. I think I solved my leg problem.
All I did was make an adjustment to my pedaling technique. It seems that in an effort to keep my cadence up over 90, I had developed an uneven pedal stroke, where I was putting too much stress on my thigh muscles. I noticed it on a hill where I was sort of ratcheting up instead of moving smoothly, and my thighs were starting to burn. As soon as I started concentrating on pulling with my hamstrings (scraping mud off the foot motion), and keeping the power even all the way around, I immediately noticed a big difference. That's all it took. Today was a personal best in distance and speed, despite a nasty head wind on the way home.
My ride was pure pleasure. I played 'A' league racquetball for years and never came close to the cardio fitness level I'm at now...from two months of training! I love cycling. Thanks for the encouragement and information.
Rick