Other people have done similar tests and published the results, see the following links.
I wanted confidence from doing the tests myself, and I wasn't necessarily asking the same question as some other tests.
My own post about this test
DA lenses on Full Frame: Test Shots thread
My post to the above thread
RiceHigh's Pentax Blog:
Compatibility of DA Lenses on Full Frame
Karl Knipser - Flickr Set
Many test photos of Pentax lenses on both film and a Canon EOS 5D Mark III
AMMouse aka Pentax_Prime - photobucket:
Some Pentax lenses on a Pentax Z-1p film camera
Wallace Koopmans Artlog:
Pentax Full Frame and APS-c Lenses
What I really want to know is how useful my current lenses will be if Pentax launches a K-mount camera with a 36mm by 24mm ("Full Frame" or "FF") sensor. Hence whether I will initially have to buy additional lenses for particular types of photography if I buy that camera.
I can't determine that, given the unknowns, so I've tried to answer a simpler question: "how useful are my current lenses on a K-mount 35mm film camera?"
Method and discussion
Briefly, I loaded films into a Pentax film SLR, attached 6 DA and DA* lenses in turn, and photographed a brick wall and a simple test target. I had the films commercially processed and scanned, and uploaded the images to where they can be reached from the links near the bottom of this page.
There are more details of the method here:
And a set of related topics are discussed here:
I tested all my (Pentax) DA and DA* lenses.
The scans and some analysis are at the following pages, one page per lens. Each image has a rectangle corresponding to an APS-C sensor superimposed.