Yes you can link the two ranges. Keith Lancaster did this on a daytrip from Du Cane Hut back in 1946. See -
http://dveltkamp.customer.netspace.net. ... eserve.htmSounds like you should do this as a daywalk - because of the boulder hopping, rock scrambling and scrub.
Ordinarily - it is much easier to go via the Overland Track - eg from Pelion Gap to Du Cane Gap. I have gone from Mt Massif, dropping off the Du Cane Range and going cross country to near Kia Ora Hut and then climbing Ossa via the track. This was one day during a long trip, and was not too hard. On the trip we camped on Massif and the next night camped on Ossa.
Dave