Well the link you posted was a good start. I did some Googling and found several different methods of attempting this. I then stumbled upon a post on the Eve support forums and modified the code to work within UBB. I tested it in IE-6 and FF and it works in both but I can't test it in any other browsers so if anyone else tries this let us know that you verified that it works or not. Don't be impressed - I read a lot and try many times until something works or I step in shyt!
I hope someone else finds this helpful too.
.post_inner img{
max-width:650px;
width: expression(this.width > 650 ? 650: true);
} 
