When the default inventory is full and you have an item set to above the normal, you cannot pick up any more items. Example would be if you have an inventory with 16 snowballs in each slot and snowballs set to stack to 64. Any snowballs on the ground will not be picked up.

I'm not really sure if there is an efficient way to do this, but it would be very useful.

I don't believe this will ever be possible on the bukkit/spigot side, so I'm closing this.