This as well as viewing other displays and cockpit areas has long been an issue for me. My solution is aided with a keyboard which has additional function keys (logitech G910) and macros - I do not have a Track IR. What I now do is to assign a snap view to each display - including the HUD.... and then assign one of my additional function keys to switch between snap view and normal view. This allows a one-click (versus having to hold down a key combo).... and while not optimal allows me to get a full screen view of HUD, or an MFCD and then back to normal.... I do wish that ED would consider some easier setup for snap view - I do this for each sim. Not ideal when closing on a target a mile away or so, but it works for me. So in short - if I need to close-up on the HUD, I hit func key with left hand... right hitting a num key... and then when done, rehit the func key to get back to normal.
