need some joist hangers for a 2.6 span of the new bathroom floor,,, as its not a long span ive seen some that say light duty,,, but what is the differance,,, my reason for asking is the bath i have is 1800mm and very heavy.. so i was thinking of doubling up the joists under the bath,, but not to certain of the differance in strength of a light weight and a heavy weight hanger,,, my plan is to space the joists at 400 centers,,, the joist on the drawings are 6x2 c16 any advice ?