masonry gallery max-width?

Hi,

Is it possible to make the masonry gallery have a max-width?
I have used this section-id css

/* Masonry Gallery  */
#max-gallery-id {
  max-width: 940px !important;
  margin-left: auto !important;
margin-right: auto !important;
  } 

which works apart from the body background is the wrong colour, ideally I want to put it in a colour_section or 1/1 element but the above css only works outside of an element

any tips?

Thanks