New fans came - did various testing. In all scenario's, with a good push fan (160cfm min), adding a pull fan only lowers temps 1-2C.
Open case? closed case? Push/Push? Pull/Pull??? Push/Pull?
Open case. Push/pull. Tried various setups, if you have a good push (stock or delta), pull had almost no effect.
On a side note, I bought a 4 pack of the Delta's and have some extra now if anyone is interested.