Dreamland......flaps full speed is 177ts for sure,and as someone has suggested ,to revert to selected speed then go back managed is a practice many use,including myself.....and there is I beleive a limit on the GS mini and how far it will go(will try to find that out)....the problem I see is during very gusty strong winds is that even with the GS mini at its max....the resulting fluctuating airspeed puts you so close to the flaps full speed limitation(177kts) resulting,obviously, in the overspeed horn.
These occasions do not happen very often,but they certainly get your attention.In the app phase the managed speed target is the mini ground speed target computed by the flight guidance(FG)part of the FMGS...