I now have a de-baffled (is that a word?) DA* 60-250mm f/4 lens. I've started to do some systematic testing on the K-1 at FF. I'm posting to this thread at DPReview:
Tests of de-baffled 60-250mm on K-1 at FF
My summary so far, based on the tests and conclusions in the 2nd post in that thread, is:
I now view this as a good 135-250mm f/4 FF lens:
At 135mm, it is good at FF at f/8.
At 200mm, it is good at FF at f/5.6.
At 250mm, it is good at FF at f/4.
It improves on stopping down.
I have better and lighter lenses covering the range wider than 135mm:
At 60mm, it is best seen as an APS-C lens, and never becomes a plausible FF lens.
At 85mm, it is just about OK as an FF lens at f/11.
Other people, with different standards for different purposes, will probably disagree!
I expect to continue with tests and field experience, and then will add to that thread.
For interest, I used
a "non-destructive" form of debaffling. I could restore it to its original state in perhaps less than an hour.