I really don't know what the original A590 or other cases look like. The ACA500 "flat" design was a very tight fit in board routing, and I hardly have the chance to move mounting holes anywhere else. Reason for this "tight fit" was that I tried to move the ACA1232 position as far back as possible, so it ends about where the A500 ends.
On the previous design, I thought it's OK when the ACA1232 is pushing a little further back, because there are cables pointing out of the A500's back anyway.
The "flat" sample PCB will arrive sometime next week - I'm happy to publish pictures that show how far back an A1200 accelerator will reach.
Yes, I'll do my best to make a case unnecessary. I never had an Amiga-related project where I had to make a total of three substantially different prototypes - I did not plan this kind of expenses, and there's other things that cost money that I haven't published yet - some software, and some hardware features that I know will work, but haven't verified them in real life yet.