There may be plenty of people who hook and tail rattlers as you do. They may consider this method to be safe because they are skilled at doing it. But I was taught to never touch vipers or pit vipers, unless they are tubed, due to the speed of their strike. The safer alternative is to use 2 hooks when 1 is not enough (heavy or wiggly snake).

Your fence post hook sounds like it might be heavier than ideal. If it is much heavier than a commercial hook I would consider it too heavy. The more quickly and easily you can manipulate hooks, the more effective and therefore safer you will be. Consider making hooks from old golf clubs, which can be found for practically nothing. Also consider making a pair of much smaller hooks. They will work better on small rattlers.