So I learned something new about Hyper-V.  The IDE controller acts just like an old school IDE controller, meaning that you are limited to 2 devices per channel.  They recommend using the SCSI controller for all your storage disks.  The SCSI controller can have 64.  Read both articles.  Worth reading.
https://www.petri.com/hyper-v-virtual-machine-storage-controllers-overview

Recommended settings - worth reading - short too...
http://hyper-v-backup.backupchain.com/hyper-v-ide-or-scsi-whats-performing-better-faster/