dont know about express but in atleast one other indian carrier from the gulf there is this procedure wherein cabin baggage of the passengers is taken from them before entering the aircraft and put in the cargo hold below. reason being they also carry a duty free bag and there is no space left in the overhead bins. now for load and trim purposes, this cabin bag is not weighed but a general rule of 7 kgs per passenger is applied. however the duty free bag itself weighs around 5-7 kg plus the oiginal cabin baggage whose weight is calculated as 7 kg but most of the times could exceed that too...so for a 100 odd passengers you end up with 700kg of extra weight not mentioned anywhere on the trim and all carriers also carry out tankering so even if you are landing at mlw , you most certainly end up 1t-2t over that.