You don't have to change any host adapter IDs - as long as they behave (device name wise) you can use as many controllers as you have slots. (Each SCSI chains has its own IDs.)
The A2090 however doesn't behave especially nicely, so I wouldn't bet anything on using multiple cards... But of course you can set up up to 7 SCSI and 2 MFM :lol: drives as amigadave posted.
