I'm pretty sure that was possible in earlier versions of MED. For some reason, unknown to us commoners, it was lost in an upgrade.
But a workaround may be to export the model in ASC and then append the frames.
But guess what?
You can't do that in the latest upgrade.
I keep V.6.171 on my desktop for that purpose and for skinning. I find skinning to be much easier in the older version.
At some time in the future "upgrade" will become a curse word.