Thanks for that John, I am somewhat reassured.
I sent an email to Langrex pointing out my concerns and had a reply from James Rhodes. He also assured me that the CV1326 was the
direct replacement for the AC4/Pen but said he would still refund me upon return of the CV1326s if I so wished. How is that for good service!
My concern came from lists that say the CV1326 is equivalent to several different valves that I know are, although similar, not the same.