By what?
It's welded rectangular tubing, that's not all that exotic and I've seen lots of that. And gusseting is easily seen in pictures. I would expect the wall thickness to be substantially higher than what the factory K's have, to make up for the loss in cross sectional area vs the factory K.
I'm sure they're well made, I've never said they aren't. That goes along with all the happy customers and lack of documented failures. But that doesn't mean the strength questions are invalid either. Unfortunately I don't think anyone is doing an FEA of the factory components or any of the coil over conversions, so objective comparisons aren't going to happen.
