6D: Lens adaptors, focus confirm chips, etc.

[simonm]

I used to be a Pentax user years ago. After switching to Canon and going digital I kept a number of favourite Pentax lenses, including a 50/1.4 which I'd love to use it on my 6D, for video mainly.

My original Canon was a 30D. For that (for stills) I had a cheap PK-Canon mount adaptor with a focus-confirm chip. It worked beautifully, although the thin extra metal layer over the mount did prevent infininty focus on shorter lenses (such as the 50mm).

Question: are there issues with lens adaptors (with a focus-confirm chip) and later Canon bodies such as the 6D+ML?

I am very nervous of trying it on the 6D: I've been told the full-frame mirror will hit the stop-down lever on the back of the lens. But...

... I have an excellent camera repairer only a few streets from where I live. He would strip/modify the Pentax lens (to dismantle the auto-stop-down mechanics, and machine away the mechanical guard on the back of the lens). Doing the machining would irreversably damage the lens's value as a Pentax collectors' item, so obviously I don't want to do it if it'll be a waste of time.

I can't use extension tubes in this application (yes, they'd eliminate the problem), as I'd lose too much distance focus. I already can't get infinity because of the adapter, but this isn't a real nuisance for video, as one reason to use a fast lens is the bokeh.

Last resort is probably to find something recent with manual rings that will fit without an adaptor, but it would be a shame!

Any thoughts on this appreciated.