Stone, Well done!!Congratulation on your new ultra expensive processing 70mm tank! I had serious thoughts that I'm crazy sometimes, but you won this time!!! :-)))))
Yes, you are actually cutting 46mm wide centre part of the film, so both perforations are off. If you have 70mm unperforated film, you can make 120 or 220 format too. With perforated 70mm you are short 1mm or you are OK if you don't mind having some perforations on the edges of your picture.