I blew off Tony H's question when I first read it, thinking "read the manual."  I have since read the manuals carefully and flown a number of missions, and found I still don't know where there is any read-out of Nav2 information (which is really VOR, not TACAN).  At first I thought there was at least DME info on the copilot overhead DME "gauge," but later found that is NAV1, the same DME as is displayed on the HSI.  The HSI also shows NAV1 bearing, but there is no NAV2 bearing information anywhere that I can find or a way to toggle between the two.  It would really be helpful (and I think more authentic to the BUFF) to have NAV2 bearing and DME available somewhere.