I have one bike complete left, the comefords one I sold to john moffat. However the one I have was supposed to be a john reynolds bike but Dave Renham checked the numbers and can't be 100% sure either way, although it was from up that way so could be a copy without the radical pivot. It has some other probable later mods too. Some if not all the comerfords bikes had whitlock swinging arms which were oval tube, i transferred that to my current bike.
I know about the engine case cutting as reg may did my frame as a seperate thing having bought the bike from julian wigg motorcycles and ridden it for a while. I still have one untouched frame which would be a great donor for a super special frame chop, and I have always fancied the seperate pivot points as described by pedrionica above. Would imagine that the rear of the engine would still need supporting somehow.
Dave Thorpe at the time questioned the purpose of the gain of moving the pivot point forward but i'm sure it was a benefit in more than a couple of ways.
will try to post photos soon.
Richard Allen had the bike in the photo i posted above, think he bought it from comerfords (?) and I got to ride it once in a trial in wales in the 90's ACU twinshock series (as was Falcon I think). Definately had longer shocks maybe 14.5". Pretty sure this is the same bike Bultaco uk are selling.