Mount manager: can I avoid automatic drive letter assignment?

Hello there,
I’m toying with virtual volumes and I’d like to achieve following: I want to request volume creation from user mode and mount it to a file system folder (e.g. d:\mounts\blah1), and I want this to be PnP-based.
I started with WDK samples (toaster, virtual volume). I can create volumes in PnP manner, volumes are memory-backed and dummy-formatted as FAT. When I initiate volume creation, I get E: drive, F: drive, …, I can use those as any other volume. Next, I played with IOCTL_MOUNTDEV_QUERY_SUGGESTED_LINK_NAME and got the volume mounted as e.g. W: instead of next letter available, but that’s it. I didn’t find a way to prevent automatic drive letter assignment. Is it possible to do that? To be clear: I want the volume to be created without mount points - so when I run e.g. mountvol I get the volume listed with “no mount points” message. No drive letter or such.
I can kind-a achieve that by doing “mountvol /N” (or maybe sending corresponding IOCTL to mount manager) before device creation, but it does not seem to be the best way of doing things, I hoped I would be able to do this as part of device-specific mount manager interaction.

Thanks,
L.