You should talk to Corsa too. He has one on his Caterham but was unsure about the merits of it being on the 500. He's an experienced trackie too.
I hear my name!
Sorry, been busy last few days - working like a mad man

Yea have discussed it with a few different people and they reckon that will get the most out of the car. I have no proof to back that up lol but I am hoping the car will grip a little better out of corners and off the line. It is a lot cheaper then the turbo upgrade too
Would be interesting to see what Lagerlout has to say about it
As Hippo said, I am currently looking into that topic too.
On my Caterham it is an absolute must have!
Car is about 50% better with it.
On the 500 I am not a hundred percent sure on the topic.
Personally I am not really interested in improving the grip of the line.
Grip level once the car is rolling seems to be pretty good.
I agree that the grip level in slower corners could be better.
And a good LSD would certainly help there...
Personally I am trying to change my driving style a little and see if that helps

Other option could also be to get a better suspension setup and some nice sticky tyres.
Obviously this is only an option if you do a low milage (would be suprised if I do more than 5k miles p.a. on my Abarth)...