At the end of the day it doesn't really matter what the weight limit is as it is virtually a new weight class in the uk and makes little difference to the parts used. 1.5 may just be a number but it is a nicer, rounder number that is practically the same and is easier to put on a poster/sign or explain to an audience member. Everyone I talk to is always confused as to why it is 13.6kgs when its such an odd number. Also it appears the decision has already been made.