Was the cavitation all the time or only when trying to get up on a slalom ski? Being a big boy (230#) I won't even try getting up on a slalom. Every time I would try I could tell the boat was using all it had to get up on plane. I start on two skis and shake a leg and drop a ski. Then I can cut back and forth. Slalom is really too much for these older little jet boats. Also if it only is happening on one side then you know something isn't quite right. Seal the pump shoe to the hull really good, use a new neoprene seal on the pump shoe, verify the wear ring is good and make sure you have grease in the PTO to push the shaft back. But, if you have everything good to go you should be able to drop the hammer and take off, especially if one side has no problem.
I dig that clear scupper!
I would just drive the rivets down and re-rivet they tray down.