Issue with the Ifor Grah is that once it hits 3.5t the trailer is legally overloaded.
Drop to the floor agri lowloader. No worries. If you tow it your still not breaking anything bar tax classes/red diesel.
but only if it's on the move .... as an entity it's not registered and doesn't technically become a vehicle 'til it moves, attached to a licensed vehicle, like the agri ... can see where you're coming from though .... much kinder to be using summat that'd cope with the weight .... HD dolley under a skip'd be the way round it.
Akin to planning rules on 'movable buildings' .... fella round here used to make chicken sheds ... hit upon the loophole of no planning required if it was 'mobile' .... started putting wheels on the bottoms of the uprights and a guide track on the deck ... wheels have to do one full rotation once a year .... made the slab big enough to go one full rev. in one direction one year and the opposite the next ..... planners were going apesh1t with these sheds popping up all over the place

an' we're talking BIG shed, but low level. He did very nicely out of his idea .... 'til he strangled his G/F and is now doing life in Cardiff nick, sewing mailbags

... never gonna see his Porsche, Ferrari or helicopter again

