It does increase size a little, as you need to account for the extra thickness used to make the compartment wall and the inside wall of the battery pack. Additi

It does increase size a little, as you need to account for the extra thickness used to make the compartment wall and the inside wall of the battery pack. Additional constraints are that these compartments generally have to be straight-walled; you can't realisitically 'build through and around' a modular compartment like you can with an inbuilt component.