re: Penrose Box

Shit Splint, you trying to outdo me for the longest post... I try to outdo Australia Post, who take on average 2 weeks to deliver any mail I send to my next door neighbour (we don't speak cordially... only over vino), but you are making Castaways's FEDX service look like Amazon's next day delivery... great job!

That corner joinery is something else... not implying that no one else has ever used them, however, I haven't seen anyone else get off their arses to explain/show them in detail... great, and on behalf of the silent majority... thanks.
Actually there are too many highlights to elucidate, if I want to make it to Christmas drinks.

Late EDIT:
This comment probably took twice as long to write as your entire project.  Your router jig,

rang bells and I made a beeline down to the workshop, found my thingo,

but then stupidly tried to find the manual for how to use it and after hours of searching, continued this typing.  I picked up about 17 years ago from Carbatec before my move to Churchill, used once and shelved... Once found online and named, I managed to download the manual and after RTFMing, is similar to your jig, but adjustable/reusable... just don't (anyone) dare ask me how to use it.

Sad to see you ran out of paint... you could've Photo-Shopped it,