Hmmm...well, I'm at a loss...guess we'll have to wait for Whitenoise to visit the forums again and tell us how s/he did it if someone else doesn't post first...but since s/he mentioned

I had to modify class.video_thumb.php
I'd keep looking there to see what else might need tweaking.

Maybe if the only thing you change is this:

Code:
unlink($thumb_folder . '/3_' . $t_info['vid'] . ".jpg");
by adding below it

Code:
unlink($thumb_folder . '/4_' . $t_info['vid'] . ".jpg");
unlink($thumb_folder . '/5_' . $t_info['vid'] . ".jpg");