Thanks for finding that name. I thought it was on the tip of my tongue but I wasn't close. I distinctly remember the "quality" of the attractions there, as my brother, friends, and I took many a chipped tooth/bruised forehead. If I recall, there was a "kiddy" slide and an "advanced" slide. As you alluded to, the "advanced" slide was a test in mat control, and failing that, your ability to defy gravity and the will of Neptune.
eta: and Mojo, yeah I remember some of those Pearl HS kids laughing at our asses ending up under mats flailing at the bottom of the slide.
2nd eta: Sorry going circular on topics here, but how could I forget the misery of standing in line with my folks for what seemed like days to eat in Morrison's Cafeteria in Metrocenter, with all that 17ing other amazing stuff around. Those never ending, winding walls leading to crappy food might as well have been the Minotaur's Lair for a child.