Oops, posted prematurely.
My two suggestions:
1) The springs feel like they might pop out, because they're bowed out. Perhaps it might be good to angle the top arm slightly down so that the springs are straighter it'd feel less precarious. Though since the springs haven't popped out yet, this may not be necessary. I also
thought about running a pin through the spring, but that'd make it harder to squeeze the arms together (ouch!). But perhaps it'd be worth putting some little bumps into the middle of where the springs go, to help hold them in place?
2) It's a little tricky feeding the filament into the hole, since
it feeds in through a socket that makes it hard to see the hole. I used the end of a drill bit to bevel the top of the hole, which I think makes it a little easier to feed the filament in. You might want to bevel the top of the hole the same way the screw holes are beveled (so the counter-sunk screw
s are flush).