Evostar 80ED and 0.8x reducer, lack of focus-cause?

[larsmn]

Hi, have an Skywatcher AltAz goto with an Evostar 80ED I used for the last couple of years. The first shots was taken without a reducer, but since I had coma etc, I got SkyW 0.8x one.  And after that I not been fully satisfied with details, though I uses a Batinov mask to focus.  Then on a sale I got me a William Optics P-Flat 4  with variable back focus (66-88 mm). Which does not focus at all.

When turning the 80ED focuser to it's inner-most position, I still hasn't any focus in the the camera, though having a +66 mm distance to the sensor (Sony Nex-5R). Like if prime focus with the WO P-Flat is inside the 80ED. Which got me wondering if I can have some problem also affecting the SkyW reducer, though having the recommended 56 mm distance, back reducer to the sensor. Am adding a M42 without reducer below and an M17 taken with the reducer (sorry about the extra text, but they are to an astro "picturebook").  Both are 30 sec exposures, approx. 100 subs each and using the same dark, flats and bias. As seen the M42 has far more detail. 

Anyone with any idea whats my problem, not getting focus ?

   

[larsmn]

PS.  The picture says M42 is reduced, that is a typo, it's not DS.