Nice to see you on this forum, I love your packs, but I have to agree with hillhater.
In my testing of A123 pouches my first design was a block between every tab in a 3P pack (I used aluminium but I'm going to peak at 1000A not 4000A, you may have seen my crappy pictures on diyelectriccar) the voltage drop was much higher than expected, the cells were doing just fine, but it was the hundreds of extra connections each one has a tiny resistance but you add them all up and it's significant.
This was a big enough problem in my testing that I redesigned my connection method. Instead of 7 blocks making up a 3P series connection, I now have 3 blocks, two of them being outside clamps and now only one block is between the series groups, the tabs in each 3P set are all sandwiched together.
I'm not saying your method won't work, it's going to work, and it's going to work pretty well, but I think it could work better. (not from theory, from testing)
I know you don't like A123 cells, but laser welding has nothing to do with the issues that hillhater is trying to point out.
When you get the car on the track make sure you have a logging method for the battery voltage, I would suggest something at the + and - battery terminals and not at the Shiva terminals (or the shiva itself) as there will be so much noise and ripple there it's hard to say how accurate the voltage reading would be. I'll bet you a cold Canadian beer that you experience higher sag at the battery terminals than you are expecting, and it won't be the fault of your cells it will be all of the series connections contributing to significant sag at peak current.