I see your point about the angled bridge, the Firebust Strat I showed is the only HSH rout guitar I have with an angle single in the bridge. So maybe that's the trick, find a SSS guitar in the showcase and get it routed to HSH?

It looks to me like a single would fit in a humbucker route straight (like a neck pup). My "Raven" (the black dye rear rout) is at my guitar tech getting milled/dressed so I can't try it now but as you said a rear rout is not really a practical example. I sent an email to Warmoth mentioning this thread so hopefully we can get some input from them also. Here is my Mighty Mite HSH, it is possible they rout theirs a different size: