Successfully complete all Thrasher and Skateboard Magazine challenges; Death Races;
and Demo, Street, and Tranny contests. Slappy will give you the keys to Reg's mini-
ramp. It is located behind the drop into the park, where the game starts. Go into 
the warehouse area, and move some dumpsters to reach it.
Note: It is actually a small bowl/pool area, and not a ramp.