Good wall - nice red herrings. Never heard of any of the paradox group, but that's just my ignorance. Well-designed puzzle: thanks!

Thanks Ross. Because of my background I come across them all the time. Never used them before because of the ‘Too obscure’ complaint. Originally had Bootstrap as one to give it away to Whovians but then all 4 turned out to be herrings so I held onto them.

OK BD - you did it! my brain is on fire trying to get my head around some of those Abilene and Cantor examples. Obscure isn't always bad because it makes you go and educate yourself and these grids are good for that as well as just for fun - so thanks for setting my brain alight

Thanks Giggsy. Wiki does a good page on the general subject with links going off to more detailed pages and sites. 8 hours later - you're sectionable.