I am just wondering what the limits for the packages are? Like, they can be no bigger than "X". Can I mix K9 items and the handler items in the same box? Can I use any mailing service? Example: USPS, FEDEX,UPS, etc. or is there a specific one I have to use. And what happens if I get everything ready, and lets say I get stuff for a woman handler and you give me a guys name? Thank you!