Any thoughts on doing the accumulation/buffering on the DC side of the PC-PSU (to avoid the extra up-down conversion)? If the device in question is a fairly low-power headless server which could be made from notebook parts? On the surface it seems relatively simple (notebook vendors do it all the time), which means it's probably ridiculously difficult.

(I know, this is for a setup with only a few devices in need of backup, which is not what the article was about, but since we're on the topic of UPSs ...)