I don't think a player will detect a 1/50th of a sec error

If it results in the ball passing through the flipper when moving really fast, he will.

In that quote, I was thinking of error
in deflection angle. I should maybe have written that out.
Just before that sentence I wrote:
I assume that you are just trying to detect collision
And then tried to describe an approach that detects ball and flipper collision even if they move through/passed each other in a single frame update! I can however understand if it was a bit difficult to decipher my explanation without any pictures to accompany it

I still think it is a quite simple, straightforward solution that should be quite fast as well. The actual deflection angle should be no more difficult than any other bounce in the flipper table.