Hi Everyone 
We have a 7.5hour layover in Paris en route to the United States.  We fly in from Naples Italy to Charles de Gaulle airport at 8:30am and depart at 4:10 pm (16:10).  We are thinking that we may be able to store our carry on luggage in the airport and then take the RER B with a change to RER C out to Tour Eiffel.  We realize that storing our bags and getting to the Tour Eiffel will take around 2 hours 
My questions are as follows:
 - How long should we allow to go through security when we come back to the airport? Will  2 hrs be enough such that we arrive back by 14:00 for an 16:10 flight? We don’t want to miss our flight out .
 - Is there a walking route that may be pleasant to take around the Tour Eiffel or somewhere else we should go? Any itinerary suggestions during this very short visit are appreciated.