Thanks Wheatfield & Edvinas for your advice. Let me report my experience in case it is of help to someone.
I installed not the Katz Eye but the Shanghai version from ebay, much cheaper at US$22 incl shipping to Aust. Many have warned about scratches and dust, thankfully I found installation not so scary. I was quite nervous on the 1st pass, but when I found a few bits of dust I was confident enough to take it out blow off and reinstall all in 3 minutes. All clean now
My lenses that didn't need AF adjustment still don't. The ones that did need some have to be redone, so it's academic to ask whether to leave AF adjustment as was or reset to zero.
Most interesting is I've found with this focus screen my K20D's AF is SIGNIFICANTLY more accurate in terms of focusing on the spot I want it to focus. It feels almost like spot focus that I've wanted all along.
On manual focus it suffers a tiny bit of misalignment i.e. shooting AF is spot on but if I use quickshift to line up perfectly the split image then the pic comes out with slight front-focus. I didn't see any shim in there so can't use a thinner shim to negate this front-focus. Any advice please?
Only negative comment is I wish Pentax had designed the holding frame with positive-feel "guides" where the screen is to sit in. As it is the screen seemed to sit loose on the frame, nothing to instill confidence that it was in its proper position before I latched the frame back.
Cheers
Last edited by Kguru; 05-10-2009 at 10:02 AM.