I'm aware this is an old thread, but couldn't find any other posts documenting Pentax lens compatibility with the Lens Turbo II.
I got mine today, as part of my hopes to get full-frame-like wide-angle using old lenses, but alas, all 28mm lenses I tried seemed to make contact with the rear element...
Well, at least my fisheye worked, which is nice.
Update: I originally labeled the Auto Chinon MC 28mm as "not working", but I have since modified it in a reversible way to make it work with the LT2. I'll start a new thread about how to do that.
Lenses I tested & results:
Working
Pentax K 17mm F/4 fisheye
Pentax K 55mm F/1.8
Pentax-M 135mm F/3.5
Pentax-A 50mm F/1.7
Auto Chinon Zoom MC 35-200mm F/4-5.6
Basically any lens where the rear element does not protrude from the mount should work fine.
Not Working fully (not focusing to infinity due to rear-element-collision)
Pentax K 28mm F/3.5
Pentax M 28mm F/3.5
Working after reversible focus modification (modification process is explained
here)
Auto Chinon MC 28mm F/2.8
I'm not ready to void my warranty yet & try the shimming method. First impression of this adapter is that it's flimsy enough as it is...