Hi guys... Just a bit of info. regards to the Goldhofer low-loader - The wheels on these things are designed to be smaller, but duals on each axle for better load distribution (Well - on the real thing atleast). Another way to get a low loader, is to search for a Bruder Low loader (a plastic toy in effect) and convert it yourself, I am half way through extending one at the minute.
I can vouch for Carson trailers, I have owned carson gear, and seen many in action, they are superb, and although very pricey, they are worth every penny in my honest opinion. They are constructed out of Alum. mostly, all machined and ready to assemble.
The tipper's are particularly impressive, when in operation.
A great place, with good prices is - mbs...
https://www.mbs-modellbaushop.com/modellbau/rc-trucks-u2/ i order here quite regular, the shipping is super, and rather quick too.
Hope this helps