PS - The envelopes are cardboard envelopes just like the other overnight services - you have to make sure you get the one that says specifically on it - Flat Rate on it and excuse me I have to correct what I said.  I said it was Priority Mail - do not get that one - it is charged by weight/zone.  It is called Express Mail on the envelope - and it says Flat Rate.  These can be found in the lobby in all post offices and the confirmation slips again are over in the lobby by the certified mail slips.  I really think that my clients are liking this method as it is just as traceable as fed x or airborne and just as fast as their 2 day service and alot cheaper.  I personally charge a few dollars over the cost of the postage and confirmation cost to cover my labels and printing costs and a little towards packaging time.  I list it on my fee list at the bottom of my retrieval fees as additional flat rate charge to the service fee for certified copy orders.  I hope this too can help your business!