Looks as if the OP may have already decided the Bushtec is his choice. And there is no doubt the Bushtec is a great trailer. A few pros and cons but none the less a great choice. I am only commenting because of DDL's post with what appears to be a bad experience he had with a ZZ Trailer. I'm not a metallurgist and have know ideal on the effects of a horizontal verse a vertical hole drilled through a round pipe and how it is affected by stresses. I would think the composition of the pipe metallurgy would be a factor also. With that said here is my experience.
In 2016 I purchased a 2008 Hannigan Sierra from an individual in Norman Oklahoma, I live in Houston Texas and rode to Norman to pick it up. An 8 year old trailer I purchased.
The first picture is the day I picked the trailer up, the next is the trailer tub off the frame going to get painted and the next two are the trailer frame. The same picture DDL posted and quoted as being from Hannigan's website, just not true. This is an 8 year old frame, yes the black square mid pipe rail is a round to flat adapter/cushion with a vertical hole through the pipe for securing the trailer tub to the tongue/frame. I have posted this picture on this forum before because someone had inquired about the Sierra frame and I just happened to have a picture.
The trailer after new paint job.
These next pictures are just testament by landmarks to how far this 8 year old trailer has been dragged from Houston Texas.
I have loaded this trailer that produced tail wag. But as soon as tail wag presented itself, I pulled to a stop and re-adjusted the load. This happened very few times and you learn as you go and make the necessary adjustments with your loading arrangements. I have always carried an 60 quart igloo positioned over the axle with the rest packed to the gills with luggage. This trailer has always been an excellent pull.
After experiencing Tom Finch's commentary on this forum, I sought a Tailwind. His engineering prowess, brilliance and dedicated expertise with motorcycling trailering is unrivaled on this forum, probably one of the greatest missed members on this forum, RIP Mr. Finch. This is not meant as any dis-respect to any other deceased members, just my self experience.
I purchased a used 2011 Tailwind in December of 2018. A significant better chassis under the trailer tub as shown in DDL's post. Still carry a 60 quart igloo over the axle in this trailer. Easier to load/unload, plus a on-board air compressor and a shock absorbent trailer tongue. The design of this trailer prohibits loads shifting to the rear contributing to trailer wag. An excellent engineered and pulling trailer.
In 2022 I purchased another 2011 Tailwind, but made with carbon fiber
My point is showing one failure of a particular design doesn't prove to be an inferior design, maybe there are other factors with the failure that DDL experienced. If the bolt installed in a vertical drilled hole in a round trailer tongue is a design flaw, wouldn't there be much more evidence and complaints on this design or trailer manufacturer. Both these trailers have served my needs without complaint.