Traveling outside Schengen

My wife and I from the USA have multi-entry visas that are valid through July. We have applied for the permesso di soggiorno and have the postal receipts. We need to travel to the USA for one week in March, even before our questura appointment. We have to change planes in a Frankfurt on leaving and fly straight to Rome on the way back. Will we have any trouble traveling with just the postal receipt? I think since our visas are valid it should not be a problem, correct?
Thank you!

I just had a similar issue.  I am a US citizen with an elective residency visa.  I registered in June and had my Questura appointment in October.  I needed to return to the US for surgery in December.  I had not received my Permesso.  I was told by the US embassy and an Italian lawyer that I "should" be OK if 1) I had my post office receipt and 2) my return flight was directly into Italy without stopping in a Schengen country.
I returned this week into Milan.  Customs asked no questions; they did not ask about my visa, or my prior trips in and out of Italy. They just stamped my passport and waved me through.
And I just received my Permesso.
Good luck!

New topic