I followed the basics of Ompa's clip mod but I also wanted to remedy the whole issue of having to keep a head count of darts to prevent the spring/dart advancing mechanism from getting accidentally chambered. Furthermore, the whole point of a clip-system for me was to have one that I could easily change/reload even on the run. That means having a mechanism that limits the advance of darts so the darts don't pop out by themselves.
Well, here's my attempt:
my darts are about 1.5" long so the cassette case option wasn't gonna do it for me. I found some of these boxes that hold photo slides (think vacation slides before PowerPoint was invented) in my office desk. You have to dremel/cut out a divider in it. Then cut out one (short) wall and glue the lid closed.
(this one's already been messed with)

then I made a spring out of two old air-restrictors (SM3K - I think), some craft foam (black) and a piece of CPVC for the barrel advancing (platform-like) thing

Here's a cross-section of that advancing thingy (hotglue was used to attach the spring to it):

Then I constructed my "dart-limiting" mechanism. I took some 5/8" PETG (I'm actually not sure if this is really PETG, its the stuff for home aquarium use - to extend suction tubes; its got a little bit of flex). I cut out a small section on the side destined to be the top (in RED marker) - keep this piece for later (for making the 'guide' -see below. This has to be narrower than the diameter of the darts so darts don't pop through it. Then I cout out a bit from the other side destined to be the bottom (in BLUE marker). The cut out has to be large enough to allow darts through, while still leaving enough to glue to the rectangular clip "box".

I found these 1/2" straps for piping at the hardware store:

Then I glued both the "limiter" and a strap to the box. It might be easier if you also install the spring beforehand - but it didn't matter for me.
