From my own research, this is a “controversial” topic: some folks say it is required and others say not to bother.
Does it make sense to attach the house to the trailer? The weight of the house should be enough to keep it on the trailer as in, will it blow off while you’re driving down the road? No. If I’m worried about tipping over, then the house is destroyed anyway.
Tumbleweed suggests welding threaded rods onto the trailer that are then passed up through the subfloor, sole plate of the wall and a HDU5 holdown. I decided to not go this route, because I would have had to strip the paint from the trailer and I didn’t like the position of where I’d have to place the rods (too close to the interior of the house).
So what to do?
It turns out that my trailer has stake pockets for adding a railing. So my idea is to create a bracket that will clip to the bottom of the bracket and hold a threaded rod.
Here’s a video of me welding the plate and then grinding and polishing it.