Update #1: Design Overview and Internal Layout
Before I go into the actual build process I think it might be good to show a few more views of the design and how it all goes together generally. I feel that it's a bit easier to understand and illustrate with CAD views and contrasting colors.
The main structure of the enclosure is two side pieces (shown in black), and they are connected by the front and rear panels/crossbars (shown in red). I divided the design up into pieces like this in order to keep the print time down to around 10 hours for any single part, keep support material to a minimum, and allow all parts to fit on a 300x300 mm print bed. I knew that for my first prototype I would likely be reprinting a few pieces, and I didn't want to undergo a potentially 40 hour long reprint for an entire half shell if I did a split top/bottom shell design.
There are a lot of nice advantages I found to doing the frame like this. It's hard to tell from the picture, but the front panel is like a structural "C" channel, printed with the front face down on the print bed. It's really stiff! There is also a lot of corner and floor support built into the LH and RH side pieces. This stiffness is intended to withstand the cartridge insertion/ejection forces. The MVS will be bolted directly to the "floor" on the LH/RH side pieces through the factory cartridge guide/cover that comes with the MV1B.
One more note: I'm leaving out info on fasteners for now to keep this high level. I'll go into that detail during my build updates.
Next the bottom panel goes in. I originally designed it to be a CNC cut sheet of acrylic, but later I changed my mind to keep this project 100% 3D printed. I added a raised grooved track built in to the bottom panel, and also into each side structure. This will allow for a printable (or cnc cut) "firewall" (not shown) to completely isolate the PSU bay in the rear for thermal management.
Moving back to the rear panel: the tall slot on the right side of the rear panel is an inlet for cooling, and the circular cutout on the top left rear is a mount and outlet for a standard 40mm fan. I'm not sure if it's needed or not, but since I had doubts I added it. This isn't a cost saving project! Beneath the fan is a cutout for an AC female receptacle.
The large square cutout in the middle of the back panel is just for weight reduction. The PSU bolts directly to the back panel and covers up that square cutout. I'm sure many of you will see that this is a Meanwell RT-65A. It might be overkill, but it packages well here and seems more than enough for the job. It also seems to be a highly recommended PSU for this supergun.
(Apologies for the messy wiring! I am not a cable management pro. I plan to zip tie it up later. 
Once the basic frame is together the layout is pretty straightforward. The MVS motherboard (with SNK cartridge guide not shown) is represented by the green block, and the supergun is represented by the blue board. The hinge mechanism is two identical arms mounted to the LH and RH structure through a separate printed pivot bushing at both ends (only LH is shown). It allows the door to swing up and back - kind of like a front loader garbage truck (it works surprisingly well!).
Up again to the front panel, the supergun DB15 controller ports are bolted directly to the front panel, and the front power rocker switch is a snap fit. On the output side of the supergun there is an opening on the case RH side support for the A/V cable out.
My next update will start with the printing of the structure shown here and hopefully will serve to start documenting the build process.
