Gary;
Once the mast is tuned, I used cotter pins turned within the turnbuckle body. If too long then cut the ends off. I then used rigging tape or electrical tape 3m was used. With any tape, the last wrap or two was applied without any tension or the end of the tapes would become unraveling. In addition, I always put turnbuckle boot covers on as added protection. Make sure the tape does is not wrapped down over the bottom or the turnbuckle body itself as it will trap water and cause rust.
As for the rings, it was a pain to install. Never use the quick release pin particularly on the forestay as they can and will come out. I repaired a few masts and boats as a result. However if you must use a quick release pin, then drill a hole in the end and add a wire or line to tie it in place so if it came loose, it would not come out but again I was very cautios of that.