Photocopy as much as possible before you send it, like the money order, then take and photocopy the postal receipt for certified, return receipt requested, on your way home and then put the originals in an envelope and staple them to to your photocopies.
If possible, go to the office supply store and buy several sheets of very loudly colored paper to use to make photocopies. Neon green, hot pink, or goldenrod, etc. make the backup copies easy to find. And then seal it all into a gallon baggie.
Penetration? You want penetration? My Bowie Knife's blade gives 13 inches of penetration!!!