Quoted from melappels:
the popbumper wont come up anymore.
Keep in mind putting anything that is heavier then the original chains, which weigh practically nothing, could put extra strain on the pops and cause pre-mature breakage of the ornamental locks, the pop bumper mech, etc. You may also not get the same 'action' on the chain movement or more importantly the ball when in the pops. If the pop can't come FULLY UP on its own via the internal spring due to extra weight, then the ball can't properly get into the pop to trigger the skirt and be fired correctly.
I'll caution everyone about putting things on the ramps, some modder created an elaborate ornamental gear thing to put over the ramp, and only after they were done did they realize it was going to interfere with the catapult. Not saying you can't do stuff, just be cognizant of potential undesirable side effects.