Ok as for the bottom end rebuild kit I understand that it was for stuck plug issues, the top half is where the blowout issues occur. Remember the bottom of your cleanout plug is actually the bottom of your hull so all the impact you feel in chop etc. is also pounding on the bottom surface of the plug , thus the violent blow out scenario you hear about, but often the worst one is the partial blowout as it can ruin your engines from water ingestion if you are a new boater and not in tune with how your boat should handle and have the experience to realize something is terribly wrong telling you to stop and investigate not just keep driving.
As opposed to the violent blowout that actually shuts down the engines when the hatch blows open.
I have a video all about how plugs lock and how they can fail and why you NEVER know if the dogs are going to release during use, so once again I will post it just for those who do not know.
Once you see how the internal parts operate and how easily they can fail you will see why I chose to make lock the way I did.
I avoid making any large holes 9/64ths is very small so it will not compromise the strength of the parts. I designed it so you do not need to fumble around down inside the clean out tube to install them like the pin fix does, "they go on the plug before it is placed in the tube.
I make it so you can see that the dogs have engaged since the holes will not line up if they are not fully engaged in the tube and the lock can not close.
This is also for convenience out on the water, you really do not want to be fooling around out on the back of the boat in a storm or rough water trying to install a cleanout plug .
I also make an adapted set for people who have the older pin fix to make their process just as easy.
Since boating season is getting started you should watch this video if you have not seen it in the past,