I've got a 20GB 2.5" hdd in my A1200. It needs the boot partition to be less than 4G in size, and under the 4G point on the drive (I made it the first partition and 2G). After 3.5 boots, it puts in place a kicktag with the updated scsi.device driver that handles larger drives, so all remaining partitions can be any size and anywhere on the drive. This issue is similar to older PowerMacs trying to use larger drives and HFS+.
