So apparently Kevlar screens don't prevent broken windows and water damage, just catastrophic damage.
From: http://www.stormshutters.com/hurricane-screens/wind-abatement.html
"What about my windows and doors that are not in a lanai?
The Storm Catcher wind-abatement system can be used on any window or door with the understanding that you may have a broken window but your home will be protected against catastrophic loss. Yes, you may have to wipe up some water and clean up the broken glass but your house will not be subjected to the huge internal pressure build up that could cause the total loss of your home."
I'm sticking with my plywood for those windows. The screens are expensive and I hope to upgrade the plywood to the metal window guards over time.