alexban,
"We are using only idle,which is just opening the reversers."
Sorry to be pedantic here but even at idle reverse you ARE reversing a thrust stream .... therefore you are getting reverse thrust of some sort, however minor. And its not as minor as you might imagine! I guess you have to be careful around places where there is dust, sand etc because all you are doing is stirring it up for your low-slung engines to reingest.