I must admit that I solved this yesterday lunch/afternoon in between phone calls.
The key is column 1 and the top middle cube and then column 4.
Column four solves your 1/7 dilema.
It did take me two goes though.
shakers wrote:Nigel's suggestion will work, but it smacks of T&E to me!
I'd love Wayne to comfirm whether this would count as a logical deduction, or T&E...