Mine is a 1960, so it is basically a 140 with the gear moved and a different tail. Small doors and small cockpit. I have flown mine from Central Texas to Nebraska to see my parents several times and to the east coast once. I have always planned the flights with the two-hour rule in mind. After two hours, the rear is yelling for relief, so I plan all of my fuel stops two hours apart. And as I have gotten older and heavier, it hasn’t gotten any better.
Your feet are about the same level as your rear, so I think circulation or the lack of adds to the problem.