[Arran]

Ron;
Here's another thing you might experiment with on that junk cabinet for drilling holes in Bakelite, try using a drill bit metal for glass or tile. I think you may be able to use the twist drill bits anyhow but a glass bit may do a better job if you can find one the right size. I would measure where your holes need to go with a combination square and use the same to mark them on the replacement cabinet, that way the holes will be where they need to be.
As for the hot chassis in the Tropic being made in Canada I don't doubt it, but I've never seen a Canadian market set with a hot chassis. All of the hot chassis sets I've seen were imported from the U.S long after they were made. Even a scan through the Radio College Manuals doesn't show any sets with a direct power line connection to the chassis so that pretty well confirms that it must have been an electrical code stipulation.
In fact even in the U.S Philco manuals I have from 1939-42 I can't remember finding an AC/DC set with a hot chassis, but I may have missed one or two. I don't think that there was any requirement to construct sets with a floating common negative but Philco seems to have done so anyhow, why they made a Tropic model that way I have no idea but there must have been a reason at the time.
Regards
Arran