My thinking behind the panamera brakes was the weight distribution of the car is pretty much on par with the 15, my tyre sizes are equal if not bigger, coupled with the stock master cylinder I would have thought the bias would be ok. however the surface area of the pistons I did not take into account so much. S15 is around the 162mm piston area per caliper and the panamera is in the 190-205 range. Will definitely have to look into this a little more though as the pedal feel / travel etc obviously has to be right. I'm still learning but will get there in the end.

Hand brake info is great, cheers, I was not aware of that.