[bestgenman]

567 has drain tubing from the top holes to openings on the bottom of the slide.  I have tried to rod them out with solid wire without success.  A call to Creslie confirmed some do have drains but do not try to pressurize in an effort open the passage.  The pressure will separate the tubing and cause water intrusion inside the slide wall. 
Mine are still plugged and will likely stay that way.  I do clean out the pin holes very often and lots of dirt comes out with the overflow.