[smlporsche]

I agree with what's been said above but the other question to be asked is how good a driver are you really?

I'm assuming that you're referring to a track set up. Are you running in Black or Red run groups??

If you're not running in the top run groups you will not notice the 1 mm difference particularly if the rest of your suspension system is not correctly matched up to it.

Regarding the strut tower brace. In a car that is driven well (and fast) there is a huge amount of flex on our cars in the front.
A good friend of mine was the PCA national autocross champion for a few years back in the late 80's. He showed me pictures of his 944 in both a left hand and right hand hard corner and you could see the hood flex up about 1/2" on the inside corners without a brace...yeah it works!