Can we get 1 column in galleries?

The gallery column pull-down option starts at 2 but sometimes you just want a nice 1 column gallery running down the side of a post. I have a functions.php hack that forces 1 column but that’s for all posts regardless of what it’s set to. And I know that it can be changed in the HTML but I’m setting something up for a friend and would like it to be as easy to use as possible.