I'm surprised no one has mentioned the easy fudge for getting an 'over the shoulder' view. Just map the 're centre' view to your HOTAS. Now to check six, turn your head to 3 o'clock, hit 're centre', move head to 9 o'clock and you have a comfortable check six. To reduce any VR nausea shut your eyes while carrying out the procedure. Only takes about 1 second to perform :)