I like the compromise of a slot based system for storage over weight/mass/volume for storage (let that stuff affect flight systems) but I'd like to play devils-advocate for using both. I have 2 slots - a left hand and a right hand. I can carry a max of 100kg. I can carry 100kg in one hand or a 50kg item in each hand, but I can't carry 3 20kg items because I only have 2 hands. I can't carry a 100kg it's in my left hand and a 50kg it's in my right because together they are too heavy. So this system is affected by weight and capacity and the limit could be reached by either. How about 2 % totalizers (one for each) so we can factor weight for flight mechanics?