Robin, It will be ok! and congrats on the upcoming clutch
I'm having a hard time picturing what egg boxes you are using, but is it possible to hang the probe down in the middle between them? That's what I always did.
Kat's idea was good, it will let you mess with it until its right. I don't think you would really go wrong though if you put the probe in the front or back. The fan should take care of you.
Justin