Hi WJ,
I sold a bunch of the Big Momma antennas 25-plus years back. They did a better job than the cheaper "skinny coil" M-125 Antenna Specialist antennas. The stinger is longer, and the coil will take more power.
They had one fatal flaw that I encountered. The big, chrome-plated cap on the coil has a glue seal to the top edge of the gray plastic coil housing. Once that glue seal starts to come loose, rainwater will "wick" into the small gap, and fill the coil with rainwater.
Sometimes the water would corrode the coil and connections inside. If I caught it early enough and dried it out, a layer of RTV would re-seal the top cap to the cylindrical plastic coil housing, and keep it dry. Again. For a while.
The Big Momma coil would take power better than a K-40. Wasn't any such thing as a "Wilson" mobile antenna back then to compare it to. It was famous for giving you a great impedance match when mounted to a (metal) trunk lid. Not all antennas would do that.
73