Hi guys. Greetings from Malta.
I see Tony's point. If all your packs are set out in side by side configuration, there is probably so little to be gained by running 3 up front and 3 at the rear, that it's not worth the hassle.
I run MR4s and my son runs TC3s. As things are we can use each other's cells.
What we do with the TC3 when we are running on anticlockwise circuits is slot in a disconnected 7th cell to bring the car up to the weight limit.
On clockwise tracks of course, the TC3 should be at an immediate disadvantage, with more weight on the outer side, so we pack all our balast on the side of the electrics. There's not much else you can do.
Regards
Joe from sunny Malta.