Do large jet transports like the 777 have an angle of attack (AOA) indicator? If so, there should be a published AOA for the best glide speed for each flap setting. AOA takes the guess work out of it.
It is an option on the 777, but I do not know how many operators display the information. Regardless, the AoA gauge information is translated into various other more suitable readouts, and we are not dealing with a FJ operating at AoA limits in normal flight.