We use "PETO" carts for all incomps. Also, packages up to 150 lbs are allowed through the ground system and up to 250lbs through the air system for some reason.. I had to deliver an engine block that weighed over 220lbs. It was marked as 130lbs on the shipping label, but someone at one of the centers had written "221lbs" in a discrete spot I didn't notice. I went to lift what I thought was a 130lb package out of my truck, and quickly realized that it was WAY more than 130... I made the workers at the business help me move it. I told them I couldn't move it alone so if I didn't get help, they weren't getting their package and would have to come pick it up at the center (I said this nicely.). they were happy to help me out.
At any rate, be conscientious of your safety and the safety of your coworkers, and don't sent irreg/+70 packages through your conveyor system unless your belts are designed to safely transport them. At my center we have long, steep slides and belts that are high above the ped walkpaths. Should a heavy package fall off the belt due to a jam or come tumbling down a tall slide, someone could be severely injured. I daresay in some instances, such as a +70 piece of steel, if it were to fall of one of our high conveyors on to someone walking underneath it would be life threatening.
Use your best judgement. A lot of UPSers (especially newbies) take our safety for granted, and fail to realize that our jobs are actually pretty dangerous, and people have died in service of UPS. There's a reason these safety rules and regs exist. I don't get paid enough to die or become paralyzed.