Where the main sheet tackle connects to the boom, I would think. I don’t remove the main sheet tackle when I derig for trailering. The main sheet actually downhauls the boom in the cradle and i wrap the excess sheet around both boom and mast to hold the boom up. Ditto with the boom vang. Works really well. No bounce.
Personally, I wouldn't use snap shackles anywhere I didn't need a quick release. Rarely, yet all too often, snap shackles open, at exactly the wrong time, all on their own. I would use a bow shackle, seizing it with monel seizing wire. In the old days before roller furling, we had to change sails as the conditions changed. We needed snap shackles for quick changes on the foredeck in foul weather.
Once roller furling became common, snap shackles on halyards become obsolete for cruisers, unless you are using a chute, etc.
