So as George suggested, tighten up your bridle lines.
Adjust as usual to center the ball. There will not be enough scope on the lines to allow the ball to hit either hull. Makes for a quiet night!

But if the painter is so long it allows mooring ball contact with the hulls, even with a tightened bridle,
like in caribbeangirls pic, you might need to tie off closer to the mooring ball.