I have noticed, in our very short FSO career ( March A-100) that the answer to many questions regarding ANYTHING is "it depends". The guide books help and do contain the answers to most questions but you have to know where to look. I have found that the experienced folks on "livelines" can be an invaluable asset to navigating the many, many pages of regulations. Remember though, that not all of the liveliners are in the Foreign Service. So some questions pertain to us and some don't :)
Here's an example: I had been following the thread about shipping cribs in UAB to DC for A100 training. Some people said yes, you can take them, some no. When the real answer was, "it depends". Apparently you can get permission to take a crib for your infant as long as it falls within the appropriate size, age of baby, etc. Basically they don't want you shipping conversion beds like the kind that start as a crib then transform into a toddler bed, then twin. A reasonable rule. But, you have to know who to ask and wht those rules are specifically. And, as always, the final decision is at the discretion of the tech making your orders (sigh).
Do your homework, read the manuals and ask as many questions as you want. For the most part, the FS folks are willing to help whenever they can.