Since you're already forsaking some HP EV's to run Scizor at 12 Spe, you (can) get rid of some more
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Scizor @ Choice Band
216 HP / 252 Atk / 40 Spe (or something else)
[Your original moveset]
The HP EV's still give it maximum health, allowing it to stay as healthy as possible when switching repeatedly into Stealth Rocks.