You're riding an America or Speedmaster I assume? As far as having that pain in the butt you spoke of... I know what you mean. Until I changed my seat, I could only go for an hour max before I had to get off and give my tailbone a break. I'm about your age at 58, am shorter than you are... 5'7" but weigh about the same. I should think my height (or lack thereof) made things even worse.
Anyway... I now ride with a Corbin seat and I can go all day. Of course I still have to get off for stretches and the like but my butt ain't complaining like it used to. Oh, I also should mention I have a backrest... pure luxury!!
