I've not taken the ST on a track.. but I don't really see the point in the question. You could take the ST around a corner at it's top speed if it was a long enough corner! If you were talking about a specific corner on a specific track then there may be some sort of comparison you can make...
With regards to stability, I have never once thought the ST would topple over; sliding/losing grip is much more of an issue, although the risk seems to have considerably reduced since changing the front P Zeros for ZZ3s.
I could tell you I have taken a corner on a specific dual carriageway at 70 mph (the speed limit!!) this wouldn't mean much necessarily, perhaps if I say that previously it felt twitchy at 50+ in the wet on p zeros it may have a little more weighting though

You can learn the limits of the ST for specific corners if you drive them regularly enough, and push it that bit further in good conditions with no one else on the road, hence minimising the risk of a collision should you lose grip..
Ultimately though you have to treat it with respect and know your limits, we all have them and it's not going to be clever to keep pushing past where you feel it's safe and damaging the ST, or worse, yourself!
Take it easy, you can enjoy the ST's abilities without pushing it to within moments of it's life!