I dunno; seems pointless to print an extra layer (of what, if not copper?) on the board, but I'm sure stranger things have happened.
Here's one incarnation of the same design, only double-sided:
It works out to be just under 2.75 x 3.75 inches; right about half
the size of the eBay original. The pot and input/output jacks are left off-board, to provide more flexibility ("Australia-proofing"); the TO-220 devices are along the edge of the board, so you're less restricted with regard to heatsink choices; most resistors spots are sized for Dale RN60s or similar, except a few larger ones where space was left for the big KOA/Kiwame parts; the input caps will more easily accommodate larger box caps (10mm lead spacing); I added a second LED so you can light the tube from below, and
have a more conventional power-indicator light, at the same time; otherwise, basically everything is as on the "Xiang Rong" board...