(1) there are 4 rates for letters -- not over 1 ounce, 2 ounces, 3 ounces and 3.5 ounces., yes? And if the filled letter weighs over 3.5 ounces, you must use the "large envelope" (a/k/a "flats") rate?

(2) if you use the corrugated sticky paper or the Cro-nel sticky paper to hold the chips, and put that inside an envelope (the right size), it can qualify for letter rates, as the finished letter (if done correctly) will not be over 1/4 inch?

(3) lastly (and this is the main reason for my post), is this of concern for chips sent in corrugated or Cro-nel letters: I see that under 1.0 Physical Standards for Letters > 1.2 Nonmachinable Criteria > "e. Is too rigid (does not bend easily when subjected to a transport belt tension of 40 pounds around an 11-inch diameter turn)." If so, then you must pay a 1.9 [another section] Nonmachinable Surcharge -- Surcharge per piece at single-piece rate: $0.17. Again, are corrugated or Cro-nel chip letters Nonmachinable? If they are, may you still mail them, but with 17-cents extra postage? Am I being alarmist? Is the rigid business just a technicality that the P.O. does not enforce for small mailings? Is this rigidity criteria enforced against large envelopes/flats?

Here are some key links that discuss this. On these pages, there is also an issue of flats (large envelopes) being too rigid and having to pay parcel post rates!
http://pe.usps.com/text/dmm300/101.htm#wp1039555
http://pe.usps.com/text/dmm300/133.htm#wp1045305

Thanks

Robert