https://youtu.be/p-O9HXDLsrk

Hit it with some FN 5.7×28mm!

For what it's worth, those plates are not really that light.  They're light in comparison to rifle plates, but heavy as hell in comparison with some other soft armors.  Top of the line IIIa ballistic inserts, today, are around 0.9 psf.  (For e.g., the "Alpha Elite Black" and Safariland's "Hardwire" panels.)  At 1.3lbs and 1.6lbs for a 10x12", these PE and aramid plates come out to 1.5 and 1.85psf!  Having said that, the aforementioned ultra-light IIIa panels are very, very expensive...

Am I the only one that doesn't "get" hard pistol rated armor? Other then maybe less backface deformation I don't see the advantage. You even take away one of the advantages of soft IIIa armor, which is that its flexible and therefore more comfortable and concealable. 

I have yet to find a single reason I would use hard IIIa armor over soft IIIa armor.

That same 44 Mag ammunition but fired from a 16 inch carbine would be a great demonstration how much better magnum revolver cartridges get when used in carbine.

Great point.

You're right, of course. Everything is relative. The same company sells some relatively light level III and IV plates.