Instead of having the case open like most guitar/ukulele cases do (having the entire top be a lid with hinges on one side), I decided to have the door open outward from the back of the case and slide the ukulele in lengthwise. This design minimizes the size of the waterproofing seal - cross section of back end versus cross section of top. I also included a handle and three carabiner/rope connection points - one on each side toward the back and one at the center of the front.
The case is made of 1/16" 6061 aluminum sheet with adhesive foam padding strips attached on the inside. The gasket was soft rubber weather stripping, which honestly didn't perform well. The case didn't end up being 100% waterproof, and because I used crummy glue the stripping came off soon after the case was built anyway...so the bottom line is I ended up with just a shock-proof case! All bolts are fastened with rubber washers and nylon locking nuts to help waterproof the case. The hinges, catches, and handle I got from McMaster-Carr, while everything else was custom made.
I might toss up an assortment of photos from the manufacturing process at some point, but for now I just wanted to share the final product. I'd love to hear your thoughts, suggestions, criticisms, or questions! Hope you like it!