All I can say is that the bullet really works. It's not a "magic bullet", pun intended, and I still have to have the ski moving at a good pace to drain, but it does drain at slightly lower speed and begins to gurgle sooner than without the bullet. Plus, it is supposed to reduce turbulence and thus minimize the overall resistance... These are really easy to make - can use pretty much any material: soft wood, mini cell from, construction foam, styrofoam, structural foam, etc. as long as it is easy to sand smooth and it keeps its shape. Glue it with contact cement for easy removal. Once you like it, you can probably make a more permanent version. Feel free to copy the shape and size of mine off my video for your personal use. As I measured, even just covering the concave area behind the drain seems to increase the drainage on the V10 Sport.
Still, no matter how much it drains, because the drain is higher than the lowest point in the cockpit, there is always a small mount of water left in there ...