vnconfig and a compact flash disk image

[Richard P. Williamson]

Hello,

4.10-RELEASE

I've got an image of a 32mb compact flash card that I created by

dd if=/dev/ad3 of=./sanDisk.32Mb.image

Now, I want to mount that image and check it for validity, edit
it, etc, and then get it back onto the flash card.  I've already
worked out how to get it back onto a compact flash card (dd, or
if it is gzipped, then zcat).

But how can I mount it?  The format is a 28Mb slice (a) and a 4Mb
slice (e).  I've tried 

vnconfig vn0 sanDisk.32Mb.image

and

vnconfig vn0a sanDisk.32Mb.image

but fdisk tells me 'invalid superblock' when pointed at /dev/vn0[a].

How can I mount the two slices on different mount points?  Can I
do this at all?

TIA,
rip