I started thinking about this long ago, but it's been on the back burner. I just got my bed put together, so thought I'd post what I have. Perhaps that will encourage me to keep moving on it. Parts needed: BMX size quill stem. Shock. Hoping to find a kids bike with shock at the SA today, but no luck.
I'll be using a rack with an approx 22.2mm ID tube attached as a receiver.
View from above: