I have the XX10. I've not tried it on my ST yet, however it fitted the one of the discs (can't remember which) of my GS. I couldn't tell you if the XX10 will fit the ST without trying.
I have some comments re sensitivity. Xena alarmed disc locks are known to have sensitivity issues. According to online research they have improved their game significantly however. I read that the position on the disc can have an effect on the sensitivity, which I found amusing, however I too found the alarm was going off for the hell of it way more when locked at the top part of the disc. Users commented that locking it to the bottom of the disc is far better and reduces false alarms. Surprisingly (and oddly) this is true....