actually you need to change around your smileys in the smiley manager, keep the original smileys in the generic smileys directory and all the added on smileys in the extra smileys directory. set the smiley display settings for 9 or 10 before you get the "more" button. I have done this for many peeps forums over the years.
Also there is a template modification that will allow you to do this.... see attached image...
Hmmm my way works for all themes i have tried it on but that is a very nice looking mod. There needs to be a mod that will allow users to not have to change anything and will always make sure that form doesn't extend over o.0 Im sure i could figure out how to do it Html wise but dont know the plugin side of it.