I did find a workaround, you can unscrew the silver part from the mount end of the lens and shim it inside there, mine already had a shim I could use as a template to cut more.
I have no idea where to get a shim the right size, so I cut my own from post-it notes. I think I have 3 in there, it is not quite perfect yet, but I can stop down to f/2.8 and it will be sharp focus at 8mm.
Adding a 4th post-it is too much, then there is a wee bit of extension....I will need to find some different kind of paper to shim it more accurately.

For now I am satisfied.

Hey man,

Same problem here, I was thinking about putting a 2mm spacer in between the adapter and the camera body, but I haven't had a chance to give it a shot yet. Let me know if you find a workaround too!

Hi there, with your Cosmicar/Pentax 8-48mm, are you able to focus to infinity at 8mm on the Q with your adapter?
I have the "RJ" C-Q adapter and infinity focus at 8mm is not possible unless I unscrew the lens a bit. I think that not all C-Q adapters are exactly the same register distance.