Unable to zoom into Spitfire site with head tracking

[JD-]

Hello, I have a weird problem here and just want to confirm it's expected behavior.

 

I have head tracking, and I really like how I'm able to zoom into the gunsight when I look closer to the screen.  With a BF-109 or Yak-1 I can get a full zoom level by bringing my head a couple inches closer to the screen.  For some reason, when I fly a Spitfire, the zoom doesn't go nearly as close in to the sight.  It's made it difficult to perform since it's the only plane where I have to use a separate zoom control. 

 

This seems to be intended based on watching others fly with it.  Is this due to how the sights are supposed to be used on the real thing?  I notice there's no padding underneath the sight like on some other planes.  If there's any way I can adjust this behavior, or if there's a workaround, I'd appreciate some help.