come on dude lol a plod will always allow a dark visor in sunlight as they have said for long enough the law is wrong but to obstruct the visor with tape would be a lot worse in their eyes.
i have been stopped numerous times with my simpon lid with a dark visor

and not once was it for that but cos they wanted too lol never had any probs with them and never been done but i do use a normal visor at night
however eleccy tape on the visor no matter were it s will be seen as obstructing your view similar to those peeps that spray a face on etc etc
personal choice and lots of different views but ye pays ye money ye takes ye chance