oldchina
Old Boeing Driver
"... the Lauda 004 incident comes to mind. There is still controversy about whether a high speed deployment would be survivable"
Apparently not, according to Boeing and the final report, at least not at cruise altitude. Certification tests showed it should be controllable but they were made at lower altitude. When Boeing flew the Lauda scenario in the simulator the loss of control was so rapid that there was no possibility of catching it in time.
The issue of controllability has to do with the reverser efflux effect on control surfaces at specific speed configurations.
Deployment at altitude is quite different than early climb