ISTR that every 0.1 second off your 60ft is worth at least twice that off your ET - so - all you need is a BIT more grip off the line and you should break into the 12s
I have a very accurate calculator that'll tell you exactly how much of a difference a 10nth (or any amount) will. Only thing is, when it's not on a website, no-one believes it.
Perhaps you should go along on one of Santa Pod's 'tuner' days - there's only about 100 runners AND they treat the surface with the sticky spray stuff
I don't get all of this. What's the point of increasing your grip ratio just to chase a better time? Like you would on a dyno, keep the same conditions as you tune your car and measure the difference. I calulate that by increasing the grip of a standard 20vT to an amount that Flea/ Nigel have acheived on their best runs, would yield a 13.61s run @ 100mph (that's a 2s 60ft with the same performance thereafter of a normal 20vT!).