it is possible. look at pocketmine there is playerInventory size only 40. and player see only 27 slots in inventory. So change it to 49 to fix it
I don't believe it'll work. You'd have to set it client side. By using the size function you'll just be able to pick up more items when your shown inventory is "full".
so can you explain me why client see only 27 inventory slots if you set inventory size to 40 and 36 slots if you set size to 49?
Armour slots counts as inventory slots, there may be some other thing like the hotbar that is included as well.
Yes it should work because in firsts versions before playerInventory was added to pm or MiNET the player see any cases in inventory so yes i think we can change it.