Horvath, I was thinking on how to lock them from the inside. The easiest ways I can think of have a major drawback: The door could be open, locked from the inside, then closed leaving no way in. To modify my existing to eliminate that problem would be to drill the latch and claw and use a locking pin. The pin could only pass through when the claw is latched. It could be attached to the exisitng inside link, so the handle would operate as stock with no extra buttons or levers.
Easier solution might be to start with locking latches
http://www.watsons-streetworks.com/latches_plus.html
