Okay. I actually didn't remember precisely what the problem was - Y translation is also fine. It is Z translation that causes
all the problems.
I set the airplane up on final, and froze (shift-p) the simulation, so no movement could occur. These pictures are 640x480 crops of what I was actually seeing (my res is 1600x900, a bit big to post!), so no zooming or editing other than the crop.
The basic view:

Leaning left, OK!

Standing up, OK!

Leaning back, all bad


Note how the FPM is no longer on the runway.
And it just gets silly when you lean forwards ...

This is where the misalignment comes in. If you lean forward or backwards the gun and bomb reticles and FPM will become misaligned. I think the "solution" was to use 4dof, or use the Z axis of the TrackIR for zoom rather than translation.
Compare DCS Black Shark:
Normal view

Leaning forward
