Icarus - I agree that you cannot tell the weight of a bag just by looking at it - I was merely trying to point out that on most flights that not all bags are average - some will be large and heavy and some will be smaller and lighter. In my experience large hard shell cases are usually heavier than the smaller soft types and these are both usually heavier than small holdall bags.. Not that you would use that as a basis for determining the actual weight.
As for your dislike of standard trims - Well I'm sorry - but it works very well for the Charter Flights - usually full in Summer with quick turnrounds a necessity for the three or four rotations of these aircraft.
However, at other times, when flights are not full I agree there can never be a "Standard Trim" and we will block seat rows in the cabin if necessary and adjust the baggage loading accordingly to get as close to optimum trim as possible.
