4Deck, before you go about making lots of changes check two things that can really screw up your rear views. In the TIR software profiles page under Motion Adjustment you'll see a TrueView radio button. Make sure this is NOT checked (i.e., it's also "OFF"). Now, go into AH and select Clipboard/Options/Preferences/View Options and make sure that "TrackIR Object Relative Move" is turned "OFF." Now see if your rear views work better. (Conversely, it works with both TV and TIRORM turned "On" but there's a subtle difference between the two in the way the in-game head pivots up and down so I prefer for them both to be OFF.)
Both of these selections affect the same thing and that's the way the side-to-side and fore-and-aft motions (translations) of your head are interpreted by the game and the direction in which your in-game head moves. If the selections are mismatched (one on, the other off) then those motions are reversed when looking aft (leaning your head to your right causes your in-game head to move left) which really screws things up so check those setting before switching to previous TIR drivers or getting dramatic with changes to the profile shapes.
Like the others said though, some aircraft are just hard to see behind. All the F-4U (except the -1) and the older 109s (E, F, and G2) are tough because they have shields that extend up and over the pilot's head for instance.