I wouldn't recommend changing the MOD to master, if by that you mean changing the SCSI ID to 0. HD is device 1 (SCSI 0), MOD/CF was device 6 (SCSI 5). So if it's a MOD drive you can make it 0 easy enough by changing the SCSI dip switches, on the back of the drive you had dips 1,3,4 high. 1 + 3 set SCSI 5, 4 was something to do with HD emulation I think and was normally high. So setting 1 + 3 low would set SCSI ID 0. But the 4K DB is configured for device types, area sizes, granularity. By changing the MOD from device 6 to 1, the 4K ADP DB will not be correct. Will still work, but won't be right. 4K can run forever from MOD on 6, I would leave it alone. Also, it knows not to try and run the Unixware from MOD - by setting MOD to 0, it'll start looking for Unixware.
On a reload, the 4K will try the HD PDS (area E) first, if that fails it will try MOD PDS (E), if that fails it tries HD GLA (J). GLA is last resort, it will boot but your AMO's don't work properly, it's only there to give you telephony while you work out how to fix the problem. But if it boots from MO, it can run like that for years.