SkaerE -
Anytime you have a situation where a bullet might strike a hard steel surface, ricochet is a possibility. Waverunner actually does what several people I know do, wear a soft pak over a steel strike plate. This will contain bullet "splatter" (spall) from a strike fairly well, and at the same time provide sternum area protection from knives, fists, steering columns, etc. better than the Kevlar or Spectra soft paks alone. Second Chance sells hard plates covered with Kevlar to contain spall. The most common are the T-30 steel and T-15 titanium plates and these (in theory) work just like Waverunner's combo.
Word of advice: DO NOT wear a steel strike plate on the back side of your ballistic panels! The reason for this is that for soft armor to work, the fibers need to stretch back (backface deformation) to stop the bullet. If you have a steel plate preventing this from happening, guess what.... you just took a round through your vest. Trauma plate pockets should ALWAYS be on the outside of the panel. They may be under the carrier, but never under the panel.
I highly recommend either a steel plate under a soft pak, or a SC T-30/T-15 plate. The best choice ( some $$$ though) is the T-15 plate as this will raise the protection of your sternum area to include 12 gauge slug, .30 carbine, 9mm AP, and 7.62 Tokarev, knives, ice picks, etc. all without adding more than 8 oz. of additional weight. It is covered by a Kevlar "sheath" which will contain spall/splatter. It's what I use. Not taped to my back though. [:D]