I guess everyone has seen the samples where DA* 60-250 "almost" covers FF with some dark corners.

But Pentax has a patent for a FF 60-250 lens so I thought maybe it is just the baffle at the back causing the dark corners.

So I finally got some time and disassembled mine to remove the baffle - and tested it on sony a7r. The results are pretty good! Dark corners were gone at all focal lengths.
I've noticed some light vingeting on some focal lengths wide open but no more than what I expect from any lens.
Resolution outside the APS-C zone is good as well, except maybe at 250 (but generally mine is somewhat worse at 250 than for example at 200 even on aps-c).

It is a pretty easy mod to do - just unscrew the mount (and make sure you dont loose those spring-loaded contact pins). The baffle is just a black tube that is glued (!?) with some spots of white glue to the back of the mount.
(I find it litte weird that the baffle is just glued that way - almost like it was not part of the original design and they just figured a way do add it later.)

Apparently the glue is not strong so you should be able to easily pry it out of the mount and re-assemble the lens without it. - And you'll have your FF lens ready.

Mod is fully reversible, as you can just glue the baffle back in its place. I guess it's purpose is to reduce internal reflections but I did notice any problems in that regard while testing.
I tested without the hood but I guess it should be fine at least in the 90-250 range.

Anyway, it looks like the FF camera is delayed again but I thought someone might find this information useful.