I hate to hear that you have had bad luck with your lower unit. The river is always a gamble whether you will get your equipment out in one piece of not, even for seasoned veterans. Debris is always changing positions in the river. Rock shoals always stay basically the same. It comes to mind that there is a rock about the size of a volkswagon heading down river from Blue's near three creeks. That HUGE rock has changed positions through the years. That being said, the best advice I can give is to KNOW the river system you are navigating. The best time to learn the river is when it is extremely low. You can get a mental picture of every shoal on the river when it is dead low. If you don't know the river real well, use EXTREME CAUTION when navigating. Use the depth finder. If you unexpectedly come into a rock shoal, trim the motor all the way up and drift across it. I have personally not ever lost a lower unit, though I have had many hits through the years. I realize that I digress from the original question, but if you use the above advice, a skeg protector is not necessary.
Bill in Bennettsville