I work along these lines
33 long (21 ft's) - 1 tonne
693 ft of mixed tube - 1 tonne
500 mixed fittings - 1 tonne
50 13ft boards - 1 tonne
So you need to cut back where required to reach the legal 3.5 tonne. A 3.5 tonne lorry cannot legally carry an average semi on it!!
I was gobsmacked when taken to the weighbridge by VOSA off the motorway, mainly loaded with ali, at just how little a 3.5 tonne wagon actually carries!