STOP

This was my reasoning also.  The rhino lining didn't hold up, it did everywhere but on the V-channels where you need it.  On top of that, it adds a ton of drag to the boat.

What we ended up doing,....pure genius,lol,...was we took a 5 ft section of 2x6 and put 6 wheels on it.  It's a launch dolly.  

what about useing the idea that LBH mentioned but with bigger tires like turf tires from a wheel barrow or something wider. I noticed that you have lots of sand an what not, but even a launch dolly of sorts might just be the ticket

memo

If the problem is just getting down the sea wall then I would recommend mounting a couple of 6" PVC pipes to the sea wall to slide the boat down.   PVC is much slicker than wood.  I live in Orlando and with all our small lakes this is pretty standard for jet skies and jon boats. I have even seen winches mounted to the top of the sea wall in conjunction with the PVC and the boat/ ski left on the PVC as a semi permanent parking spot.