You can double the volume of ink or paint stored in the pen by removing the reservoir and filling the body. The reservoir provides a double wall of guaranteed protection, which might be what you want, but it does reduce your carrying capacity.
Other nibs you can use in this pen
Tachikawa Manga G nib fits perfectly
Insert our large nib feed to use the Zebra Manga G nib, Brause Rose, our Sketch nibs, and several Hunt nibs including the 22B, 56, and 101
Insert an adaptor to work with smaller nibs, including crowquills, Gillott 303 and Principal nibs