Before you assemble the wooden vice around your LCA and the bushings place the aluminium tube in position and place a washer over the end of the pre-formed flared end of the aluminium tube - hold this in place with tape - see first photograph. This will stop the aluminium tube from moving about and help to stop it from being pushed into the wooden jaw of your home made vice.
Place the LCA in your wooden vice - putting the end with of the unformed aluminium tube over the hole you made in the middle of your wooden vice jaw
It should look a bit like this