two thunbnails size

logically, find this:

PHP Code:

if ($width > $vboptions['attachthumbssize'] OR $height > $vboptions['attachthumbssize']) 


and put this just before:

PHP Code:

if ($width < $vboptions['attachthumbssize'])
{
    $vboptions['attachthumbssize'] = '100';
} 


so if the files are bigger, the new default for thumbnails will be lowered to your prefered size before the treatment...

...and you can count you as a lucky guy, i never give codes for free usually.. i suppose it's the time of night...