Questioner answers his own question with hack answer
Questioner decided to ignore DIY.SE advice and instead chose not to install any kind of box or approved plate and instead mounted his cable plate with molly bolts sunk into drywall.
IMO a very "harry homeowner" choice - a solution that will end up needing a new solution by someone else later.
So the question is, when answers (maybe this one maybe not) contain bad advice, beyond the simply solution of down-voting, should we do more? Especially when the answer is given by the questioner and thus is likely going to be the 'accepted' answer.