I’ll add my 2.5 cents. A strap is an easy and cheap thing to have so there’s really no excuse not to. The rear arse of a boat get a lot of bounce on the road and especially at freeway speeds. It’s like the tip of a whip. Here’s two short stories…I was trailering a small aluminum boat down in Baja. We’d been on a dirt road probably going about 8-10 mph for a few hrs taking breaks, aways going slow to be careful but at one point, I looked back and saw that my boat had bumped off the side of the trailer and was just attached at the eye. Fun times and no problems (No Problems was the name of several of my boats as there were always problems but they were always fun to fix and learn from). Just about 4 years ago I was trailering a larger fishing boat through Mexico way of San Felipe/Mexicali. After being on dirt for 20 min and pavement for about 3hrs, I had hit an unusually large (even for baja’s standards) pothole and my entire trailer popped off my ball. The safety cables being attached at the bottom of the neck/coupler ground through in less then 2 seconds. From my rear view mirror, I saw my boat sliding away getting more distant from my truck. Note that I was on a narrow 2 lane road, that was built up about 12’ above the salt flat we were crossing, and with only about 1-2 feet of shoulder before the 45 degree slope began. Essentially it was the worst place for this worst thing to happen. I was quite lucky in that I hit my breaks and semi re attached myself with the runaway trailer & boat and was able to guide it to a stop. All worked out ok in the end but it was another lesson for myself to double check all connections. The coupler was down and even had a padlock through it but either it wasn’t fully seated or there were some issues with the coupler. I have replaced all those components, purchased quality bolts, new chains, moved the chain mounting set up etc. No Problem right? A strap….why not. I have a LOT of trailer stories.