I've read that the engines on the B727 can be used in-flight - but not recommended!
One hundred percent correct. However, in the 7,000 plus I flew the 727, I never had cause to deploy the reversers in flight. One more fact about the 727-100, on a maximum performance landing, at normal landing weight, the reversers were not effective, because by the time the engines spooled back up in reverse, you were almost stopped. The brakes are that good on the 727, assuming it was well maintained.