POTENTIAL SOLUTIONS
1. It would be nice to see a ghost effect when holding your item so you can see how big it is or you could shrink the size or just and green dotted trim to your inventory so you can see where it will go and how big it is.
2. When it comes to the mater of fitting objects into your inventory when you have to correct number of slots but not orientation, perhaps an auto fit feature where you hover the item over and the space will be made for by auto moving of items or perhaps the ability to story vertical items horizontal which actually makes a lot of sense because then you can play tetris in your inventory when trying to fit items in; but a rotation feature of items would be very nice.