Thanks for your thoughts. I think once I lighten it up a bit with some changes, the prospect of folding on the go or just stowing will be more manageable. I'd still like to figure out an unobtrusive way of securing the R20 fold, like maybe a bit of bungee somehow.
It's odd that the non-folding 20 seems relatively rare--especially given the limited practicality of the folding R20. But then, as yohannrjm notes, maybe the bulk of its practicality lies in its stowability.