I put a two-inch hole in the lid. Still fairly quiet.
Lateralus, making the suspension too stiff can make it non-compliant and cause problems with the wheel not maintaining contact with the ground over bumps. Too soft and the bike wallows and is hard to control. You're looking for the middle range. There are all sorts of ins and outs involved with this kind of stuff. I'd counsel you to make small changes and keep testing thoroughly after every adjustment.