Thanks neolith, I might just take you up on that! I'm thinking of making the inside of the shells much more solid. For the inside of the front shell, I think that the area around the wells can be extruded up to the level of the top of the wells, leaving the standoffs the only part that is proud. The standoffs for mounting the board could be made larger in diameter for drilling and also to keep them from splitting from the screws. I was also thinking a surround that would position the screen in the right spot would be good. It also might be good to add just a little more to the wall thickness, as the lips are quite fragile. I'll work through what I can. Waiting on a few parts yet.
How about a separate model for the cartridge? I could then 3D toolpath cut one of those out of a contrasting material and possibly even some text and or a simple logo. I see one on Thingiverse
https://www.thingiverse.com/thing:2076431, not sure about fit though. Not sure about the battery cover yet, but maybe just use some magnets to keep it in place. These will be later on.
Yeah, it's quite and involved operation to machine one. The outsides are best done as a 3D relief toolpath with a 1.5mm ball nose tool and the insides with a straight end mill. I did a 3D toolpath on the inside, and while it worked, it does take a long time for it to raster back and forth/up and down to complete it. At least a couple of hours for each face. A mostly 2d strategy would be better on the inside. After that, then there's the sanding and finishing. By the time it's all said and done, they would be a bit pricey. There's a lot of optimization that could be done for the toolpaths, but need to get other things worked out first.