With the 10.5 & 12.0 inch worm the open vent areas want to flash a little for me. An extra clamp at midpoint helps, but doesn't completely eliminate the flashing. It is fairly easy to remove so I just pull it off; but I am not making big runs either. I use medium @ 350 degrees, normal pressure. Tails always fill out. I would rather pick flashing than have incomplete tails.