Thanks Lenny for posting that Bob trailer. I hadn't seen it before. As I look at it
I can only wonder how it would handle in tighter turns. Out in the open spaces
I'd bet it would be fine though. I like the suspension on the one in the lower picture as it bothers me having a structure as long as a bike & trailer that's rigid.

When I woke up this morning it came to me how I'd build my suspension and I've yet to create a projection drawing of it to post here. I'll do that later today.

I rendered this sketch to better visualize the layout of the trailing wheel.



I've seen those little kids riding in groups on those tiny kiddie bikes with their Mom's walking behind them. The training wheels are almost as big as the bicycle's wheels. I'm betting the wheels on those little bikes are about 15 inches or so tall.

But for me it's the front end of one of those little bikes I'd like to obtain so I could use it similar to the sketch above.