>I tried a -20 lens adjustment and it was not enough to correct >the backfocus.
Wow! That sounds crazy. How critical are your focusing parameters ? You would expect a certain amount of focus leeway would be inherant through depth of field. I appreciate lens type and exposure settings f stop values would differ. but not being able to sharpen things up all the way back to -20 sounds pretty extreme. If a third camera body doesnt correct I would deffo look for the problem elsewhere. I must admit I have had no such issues with my D7000. I thought I had focus problems during some macro shots, but even though I was in good light with a fairly fast shutter speed. It turned out to be nothing more than camera shake, catches us all out when we least expect it. Maybe its best to rely less on the technology and opt for manual focusing when things get critical. All the modern gizmos are great but they do lean towards a point and shoot mind set. I really hope your third time lucky, I know I would be pretty frustrated. Very best of luck to you.