Good progress Jaws. RE: Sock Holder; I'm sure you know that they do have premade holders, but nothing wrong with coming up with your own design. You could get the made sock holder rings and attached both socks at the end of the sump. You could use plastic brackets or acrylic screws to attach to the holders. This would take up about half or less of the space.
Again, just another option for the future in you decide to change things up and/or need a bit more room.
Edit: If you have a plastics store in your area (like a TAPS), you could also easily make the holder with acrylic. They have rings and tubs (that they'll even cut) and you can make holders that way.