All the other back armour pieces like the lapotronic pack, and the lithium pack can be shift clicked in, this one can't

To fix this it will break a lot of things, it will move all the meta data for the parts, and will need a new item

It would break all current worlds. Not going to fix

I had to add the right click to inv

it dose not extend item Armour that is why

This should be possible in 1.9, since mojang did it with skulls and pumpkins.