Using Precancels On Firstclass And Priority Mail

I don't collect precancels but use current and older ones on shipping letters and small and large packages. I have had for many years a "precancel use permit" at my PO, from which I send 99% of my mail, and have NEVER had a problem. USPS has always handled my mail properly. Today I had to discuss a returned package rejected by a receiving post office because of the mixed bulk/precancel stamps with current regular postage. I called attention to the management DMM paragraph PO23.2.0.2.1 and two upper-levels said essentially "yes, that is perfectly OK."
Does anyone have any further ideas about this, or have you had any rejections or similar problems?
Thanks

Keeping a copy of the DMM with me at all times has saved me from a lot of headaches. And I have plenty of covers that were refused at the receiving end - sent back because of re-used postage!

Peter

Thanks for the response, Peter. I have never had 'several' and this is the first truly wrong (I am quite sure) return. Will advise how this turns out.

Peter - for what this may be worth, the post office here in Green Bay was quite courteous in giving me NEW information a couple of days ago:
- mail piece must be presented to window clerk for cancellation
- precancels must meet exact amount of postage required for the piece
- 'first class' must be written/ handstamped directly below the stamps
- here is the kicker: stamps totaling more that $1 must be handstamped with mailer's initials, month and year dates and will only be valid during the month shown. whew!
I don't have the most recent DMM info so settled for above, nicely printed out with name and phone number of clerk in bulk mail dept and placed in my box.
Conclusion: using bulk mail and precancels is no longer easy but it can be done.