I forgot that the pf65 has a stop at the bottom of the collar,that prevents some eyepieces to fit all way down and sit on the collar..the pentax xf zoom,has some grooves at the bottom to fit this feature and allows for a perfect fit..I had to cut a little notch on the bottom of the older swaro astro version zoom to allow forinfinity focus..i wonder if this could be the cause..it would have a very easy solution..It is very strange though,because there is a report of a slightly modified baader mk iii reaching focus on the pf 65,so if baader improved the fit of the hardware on the mk iv it should work,at least at 20mm