Here is a little advice from someone who has made a cocktail. The kits from arcadedepot.com are a pretty good deal if that is what you are intending to build anyhow. If you have the tools and the time and enjoy the process of building something from scratch, then it might be worth designing the whole thing yourself. IF you want to build something with different dimensions than the kits, well then you need to ask yourself if what is more important, custom or quick and easy.
When I built my cocktail I ended up designing it off of kyles plans, looking at pictures from someone who made a kit from arcade depot, and a few additional modifications I made myself. I do like woodworking and do other projects besides the cab, so I enjoyed the from scratch route.