That's fairly low, for a properly drive car anyway. I'd look to raise it 5-8mm.
Take a look at this image, it's my car with the relatively firm AST kit on. Steady state cornering you can see that there is still a element of body roll, imagine yours doing the same, possibly more, and you can imagine how close the bracket will be to the tyre.
I think there is a common misconception that low = go (usual spiel about center of gravity etc). Sure to an extent, but sometimes I have customer cars turn up that are simply running on the bumpstops!!!