Yes, you can mix models to create a custom Stratocaster tone. Many players use a hot bridge pickup with vintage-style neck and middle pickups or use a mix of single coil sized humbuckers or stacks and true single coil pickups for maximum versatility.
Just ensure the pickups have compatible polarity and wind direction to avoid any out of phase issues.
For further information, contact our Customer Service and Technical Support Team: support @seymourduncan.com