I've never actually tried this, but I've been curious. The Liir cruiser PD section has a whopping 20 light mounts (I usually play Liir), so I can foresee some serious pain if loaded with pulse phasers. Or possibly even UV beamers. That would be interesting. As it is, I usually just use the PD destroyers with deep scan sections as dedicated escorts and deep scan support at my planetary garrisons. I rarely use them as ships of the line, partially because most Liir ships are liberally coated with light mounts anyway. Gives you plenty of PD.
Still, an interesting concept though. Especially for a trade escort ship, since the AIs seem to like using destroyers (including my own old decommissioned destroyers!

) as commerce raiders.