You can do 50 solo, non-stop, and in most cases do it comfortably?

You can do a supported century. Break it down into five 20 mile rides, with a 5-10 minute break in between segments. Find a group of riders at your pace. Get off the bike at the rest stops, but don't stay off too long. Long enough to stretch, refill your bottles, use the porta-potty, grab a snack. But no more than 5-10 minutes.

And don't listen to the internet heroes who'll tell you that unless you do 100 non-stop, it isn't a "real" century.