I am not saying "Yay" or "Nay" to the HF issue. All I can give is a personal perspective from my efforts to date.
"Itty-Bitty" was built on a HF 40x48 because it was the size TD I wanted at the time and I can't weld. It has served me well and with proper maintenance and inspections, it will continue to serve me into the future.
The second build never got finished. I started the "Paddy Wagon" on a used HF 4x8 compliments of Craigslist. I got the floor structure on and started the side wall profiles, and decided it really wasn't the style that I wanted. Going to go with a more traditional profile. I didn't cut doors and windows into the sidewalls I all ready had framed, added the roof and front wall skin, hung a couple of swing doors in the back and (again Thanks to Craigslist) it has found a home as equipment hauler for a local band. My trailer is a roadie!!
I do have another HF 40x48 frame that is being transformed into a mini-Cub baggage hauler. Got it for free because it had a bent tongue from overloading. Not sure what I'm going to do with that one when it's finished.
All that being said... my second tear (would this be #2 Part Deux?) is stuck in the planning stages. I'm torn between doing a Slumbercoach clone which will need a custom welded frame or an Ultralight frameless. To further cloud the issue, I have been looking at the re-prints of the old 30's through 50's magazine plans and toying with the idea of doing one of those brought up to modern specs. Decisions, Decisions!!
P.S. I really haven't given them a thorough look-see; but for a couple $$$ difference, I would probably go with the TSC for a ready made trailer frame. Just my opinion.