[galaxy-dev] Increase select multiple menu width for <param> tag type="data"

Hi, Is there a way to increase the width of a select multiple menu for a <param> tag type="data"? Certain dataset labels I have are very informative :) (i.e. long) and when used as an input to a tool you can't read what the difference is between each item unless you look at the dataset number and look back at the history. regards, Leandro