1) some fins break, when insertion and removal is repeated.
this is a mojor problem, becuase some advanced users will inevitably remove the nib and feed.
the underchannel + under fin structure design weakens certain portion of the feed significantly.
even though the combs are 0.6mm thick to compensate for loss of structural integrity of the design,
it simply isn't going to work.
2) the "tail" portion of the nib is simply too thin.
in order to use this feed with commonly available ink converters, the tail has to be very thin.
thickness is under 2.1mm in diameter.
machining additional air and ink channel will be a major challenge, as material is prone to bending.
also, additional machining will further weaken the tail. this part will be prone to breaking.
