The halo regs have not been published (at least I can't find them) but all the teams when they trialled the device had the same dimensions so there must be a template out there.
None of those renders make the halo look any better, as well as making it downright dangerous, this goes for other renders I've seen of canopies and screens. What the halo needs is free air space around the drivers head, i.e. in the event of a deceleration the driver's head doesn't hit the safety device, it would be kinda self defeating otherwise. Interestingly this is what the FIA highlighted as the main issue with Red Bull's aeroscreen, so I'm not sure why they didn't just move the reinforcing bar out to the halo dimensions - or why Red Bull didn't use the halo dimensions when designing the aeroscreen. Perhaps to wrap the screen around required a tighter curvature than the halo, or the halo is actually wider than the cockpit?
It only needs to save one life to be worthwhile, the cockpit side protection was despised (esp. Ferrari in '96) but has saved numerous drivers (Perez at Monaco immediately springs to mind) so to the HANS device. I think after a while we'll stop noticing it or at least move on the next outrage.
"There is one big friend. It is downforce. And once you have this it’s a big mate and it’s helping a lot." Robert Kubica