Sorry about not copying the List, needing to keep track which Lists adhere strictly to RFC which require "Reply To" cannot be configured to point to the List, only the OP.
The two kernels I've been using initially are direct links from the UML homepage. The fs link on the same homepage might have originally linked to other specific fs, now only points indirectly to the regular fs page. Assumed what was recommended would be a good starting point, apparently not.
I can modify pastebin settings, felt that the entire log wouldn't be particularly useful to others assuming the relevant parts would be part of the answer posted to the List. Can see if the posted answer isn't specific about the problem <maybe> the entire log might be useful.
Your verification that the 3.7.5 kernel works for you should be particularly helpful, thx.
Am hesitant to publicly suggest a systemd improvement before I can even get a single UML instance launched, but I would suggest that wherever chroot is recommended that the systemd configuration supporting file system namespaces be used instead