Haha, yep I hear ya. Short neighbourhood trail rides that used to be easy with gears now completely destroy me on a singlespeed. So. Much. Standing. And Pushing (both on the bars and up hill on foot).
I also took advice from other articles you've written and am running my chainstays as long as possible with the sliding drop-out. That extra length makes a big difference in traction, despite being such a seemingly small change.
That's wild about the tire inserts and long/slack geometry acting as a method of suspension, however simple. Far too many people over-bike. Same with automobiles. And life in general. Me included.