trailer axle gross weight

hi looking for the trailer axle gross weight for a scammell coupling single axle step frame trailer on 7.50 x 15 twin tyres on 6 stud wheels as used by unigate a long time ago, this is coupled to a Bedford oxc tractor unit with a gross design weight of 12 tons depending on the trailer tyre loadings, the gross weight of the unit is 6.7 tons, leaving a possible 5.3 ton on the trailer axle, in the Bedford manual the only trailer shown is a straight frame on single balloon type tyres (fore runner to the super singles I suppose), alan