Well, I don't consider myself a camera builder, more of a camera assembler as I leave all the precision work to those more qualified. But, since you also included "mods and creations" in the subject title, here's a pic of my 4x10 Swiss Lotus. It's assembled from bits and pieces from ARCA-SWISS and Lotus along with a few pieces of aluminim bar stock I bought at my local hardware store and cut on my table saw.
It works great, and thanks to the people at ARCA-SWISS and Lotus, is a pleasure to use. The weakest part of the design is (of course) the parts I built. There is a bit of flex in the rear standard - not bad. It reminds me of the Canham DLC I used to own. You can see it flex if you push on the top of the camera back, but once the pressure is removed, it goes right back where it should. So, don't push on the top of the camera back and everything is OK.
Using thicker bar stock would have minimizd this flex, but would have added weight (the camera, as shown weighs 6½ lbs.). Now that I've been using the camera a while and am pleased with the way it all works, I may design a better rear bracket (rigid and light) and have it fabbed by a local machine shop.