Post Import-SPWeb custom masterpage not found

I've imported an SPWeb (subweb) into a new site collection/db. I'm able to see the _layouts and other system pages (v4), but in ChangeSiteMasterPage.aspx I'm not seeing our mycustom.master in Site Master Page.

I've enabled publishing features:

• Enable-SPFeature -Identity "PublishingSite" -URL "http://intranet/apps/newsitecollection" 
• Enable-SPFeature -Identity "PublishingWeb" -URL "http://intranet/apps/newsitecollection"

I'm still seeing only v4 and nightandday in the Site Master Page dropdown, and still getting

  The file /apps/comp/_catalogs/masterpage/mycustom.master does not exist.

when I try to open the pages. I can't seem to get it to inherit from the top level site.

I've gone so far as to open SPDesigner and copy mycustom.master from the top level site to /apps/newsitecollection, but for some reason still getting the 'does not exist' error.

Any guidance?