What are you trying to achieve? that is the question.
Even if you put 20's on, you'll still have that wheel arch gap which you'll probably want to get rid of. People do put on 20s and have a decent ride, but personally I'd advise sticking with 19s (MV4 are very smart looking alloys IMO), change to NON RFT (that way you minimise cracking issues), drop the car to your desired level and throw on some spacers if you're looking for a bit of stance.
That to me says a lot more than just slapping on 20's
I think most will agree on that?!