Hi Steve & welcome to Rib Net
As far as I know what is on the DOT web site is correct, but look at the 3.5 ton limit thats wider ar 2.55M.
I dont belive it makes any difference if its tubes or steel but one option would to part deflate the tubes and pull them into the hull.
The other thing is the length at 7.00M this I belive is measured from the tow bar to the tip of the raised outboard.
One place that may be able to say 100% is http://www.indespension.co.uk
They used to do a great free book about what you can & cannot do towing, given them a call.
Saying all this I have seen many big RIBs towed, mine got delivered on a trailer at at 7.8M length & 2.7M beam was well over the limit. Even so I dont know of anyone being pulled up, maybe other know different.
Hope this helps