If you look at your first pic with both drivens side by side. Like you said the ramps are on opposite sides. Picture the belt grabbing the outside half. Spinning counter clockwise the 30 series is up against the ramp. The belt will grab and cause it to be against the ramp and move the driven forward. If you try to do thatwith the 20 series,the ouside half will spin until it hits the next ramp. This will cause the driven to open and your belt immediately drop down into the groove. You will be taking off in high gear with no torque. The spring may also come dislodged from the hole. If you replace the 20 series spring with the 30 series and clock it the same way the 30 series is setup so it sits on the correct side of the ramps it will work.