At this point, the card only adds 4MByte mem with autoconfig, and another 1MByte in $c0 area for compatibility with old A500 software. Further memory is added by the ACAtune tool. In other words: You have 5MByte fastmem on a cold-start and more memory after using ACAtune. In addition to that, you DO NOT LOSE memory if you use maprom.
Yes, there are differencies in PCMCIA handling between Kickstart versions and yes, I'm on the safe side with 4MByte-only-autoconfig. With the limited space in the logic chip, I don't want to waste too much on different Kickstart versions, because for floppy-boot-software, 5MByte fastmem is surely enough, and for HD-boot, you have more mem.
The tricky question at this point is: What will we do with the "hidden" memory areas? The ACA620 has 16MByte physical memory, where only 10MBytes are being used right now (9MBytes fastmem and 1MByte for Maprom). Toni Wilen has already made an interesting suggestion for that, which I will investigate when the final PCBs have been delivered.