change Active menu select field to larger size

we have a lot of menu items - around 350 across all the various menus. trying to find just one menu item in the Active menu select field is troublesome, especially because the "---" type marks that make it readable defeat trying to go to one item by typing the item name. (i don't doubt that it can be done but it's just difficult.)

i found it was much easier to use that field by assigning a "size" attribute (i used 20) to the field definition in context.core.inc. it still works the same way, but now instead of a giant popup list i have a box i can scroll - and search - through.

i don't know if there are something like Drupal UI guidelines that this would violate - that there is no #size for select fields in the Forms API seemed like a hint. but i figured it's worth at least asking.