Nice idea but I think I will stick with the Li-PO Pack that I have for the time being as I could not really find any quality Li-FE Packs that would fit. I did have a fair look around for them but trying to get this sorta stuff in Australia can be difficult.
From what I can see you have about as much space as I do really. My Regulator will be moved tonight and will then fit in behind the throttle Servo which is going to be replaced by the Low Profile one so everything should be a little bit more tidy.
Apart from that all should be good for weekend