I got my replacement K-5 body yesterday.
The bad new is there is a "string of pearls" on the second sensor as well.
The good news is it's lighter in color and tough to see in the vast majoirty of shots not designed to try and find the issue (i.e. "real" shots). This is in contrast to the first defect which even at f/8-11 could be seen without too much difficulty on the preview LCD of the body at 2x.
Also, the defect on the second sensor is in the lower left quadrant of the frame while the original defect was just above the center of the frame. So in terms of placement, the second defect is also an improvement. Obvisouly I would prefer it wasn't on the frame at all, but given that there is an issue, at least in a less noticable location.
So short of spinning the wheel one more time and trying a third body, I'll probably just return the first body, keep the second body and see how it goes. I have a year to send it back to Pentax if it becomes an actualy issue in my images and/or I just want to have it taken care of.
Here are the two defects, 100% crops at f/32, without the application of levels or anything to enhance them - so basically how they appear on a light background under "normal" conditions.