You need to have at least 40mm to 57mm to prevent the A-10 and Apache from closing-in on you !The A-10 (which is the class of aircraft a SHORAD will be engaging), can sustain direct impacts of rounds up to 23mm, per Wikipedia. Not the greatest source, but not the worst. The Apache (which is also a member of the class of aircraft a SHOARD will be engaging), can also sustain direct impacts of rounds up to 23mm.
Your 14.5mm SHORAD will be used to shoot down nothing but $200 kamikaze drones. Why build a whole logistics chain, as well as the vehicle itself, for such an overspecialized use? Just use the 25mm, and then use it (impactfully) on every single other target as well.
SHORAD is simply defense against incoming missiles, bombs and drones.