Found Solution. Loaded Offroad Navigator 1.7b.
The ORN altimeter seems to work quite well now that 1.7B makes the screens usable. Beware, however, about coordinate data. Since TT has locked all of the 3rd party developers out by not releasing the API/SDK for the new NavCore7 firmware, all they can get access to is "road snapped" data. If you're near a road, it'll assume you're on it. Useless for such fun and games as geocaching.
Here's hoping they go open kimono with NavCore7 as they did with prior versions and let the developers (and their customers!) who need the
raw coordinate data have some fun again. I just bought a Garmin eTrex Summit to supplement my 720's function because of this problem!