Have you ever bought two items with the intention of just putting them together and using them? I did...I bought locally a Sinar 10x8 back and frame and then bought (via mail order) a set of bellows. When they arrived I was horrified to find that they were too large for the back.
I didn't realise that the metering back was larger than the normal back and yes you have geussed...I have a standard back and metering bellows. If anyone wants to swap normal bellows for a set of metering bellows please PM me. I can supply photos direct (they are in very good condition)