I took a look at the .pdf of the Hammond case you are looking to use.
I remember looking at that case myself when I was planning for this build. I determined that the stock x0xb0x would be a tight fit and the x0xi0 would not fit at all.
So if you are looking to put an x0xb0x without the x0xi0 expansion, then it will fit.
The 3mm case depth difference is negated by the fact that your faceplate and board stack will sit more than 3mm further out the face, because of the difference in the mounting of the faceplate. You will have to shave down the standoffs to dictate the faceplate to PCA stack standoff height.
If I were planning a stock x0xb0x, I would still use the larger case though (If the cost difference is similar, sans the wood side panels) because then there would be so much wonderful space to work in some mods in the future or do a wild paint-job on. The bigger case is still fairly compact and portable (mine now weighs 8lbs with all the extra guts).
To work with the Hammond case, you will need the appropriate tools, punch, drill and metal cutter (I used a Dremil tool with cut-off wheels), a steady hand and good planning & measuring skills.
Good luck with your dream. Enjoy the build, put lots of thought into it, plan it out, do test fits at every stage and take your time. I am no expert metalworker, but I muddled though it and learned as I went. In the end you have something unique that you have created yourself. That is what I think makes a open-source kit like this so special and fun. You end up owning a musical instrument that has been build by your hands alone.............then plug it in and you have a whole new creative playground to work with