You can also save on your load time if you can send in a minimum of 18 units of any products that Amazon considers standard sized. Once you cross that 18-unit threshold, the Amazon system generally stops splitting the units up between multiple FCs and has you send them to a single FC, which makes things a lot easier. Also, you may not want to spend as much time figuring out what sets will fit into a given box ahead of time and just figure out what you want to send in. Even if you can't fit it into a single box and have to split it between 2 or 3, Amazon's shipping rates are so cheap that it doesn't make that big of a difference.