I just don't understand why.
Especially at the expense of drilling holes in your strut tops. It won't add anything measurable other than weight.
If you imagine a box without a lid this is your suspension at the moment [_]
And that with the strut brace all you are doing is putting a top on that box.
It's still going to flex unless it is triangulated in a way that fixes two opposing points, fixing the boxes dimensions by the strength of the triangulation.
You really think that the strut tops are going to move THAT MUCH under cornering on road tires? If you do, you're mental. Your tires are going to lose grip half a G before the strut tops think about flexing.
Guess what the fastest A3 on the forum, which pulls more lateral G's and has more front end grip DOESN'T have fitted? The front strut brace which was bought for it probably 6 years ago.
And on a 1.6? Really?
I don't aim to be derogatory about the car or the performance, but it's more that you're going to permanently drill holes in the strut mounts which will be irreversible. I really wouldn't recommend it at all.