As I'm sure the poster of the above knows, Part 25 certificated aircraft are tested for structural behaviour (flutter) up to VD/MD, but not above. Above VD/MD all bets are off and the designer has no more data for you. Flutter can develop in seconds and can be catastrophic in only a few more. To take the A320 as an example, MD is approximately MMO+20 knots at FL390. If you allow your aircraft a '50 knot overspeed', then you are not only conducting experimental flight test, you're doing a research programme that's unlikely to end well.
May be I formulated my point in an unclear way. So I try to rephrase, since I consider it important.
VD/MD of the A320 is 381kt / M0.89. As we usually don't fly over 340kt / M0.80, and we were talking the high level case, '50kt overspeed' is a rough ballpark just to show that you can go very far on this side of the performance.
In reality you will have an extremely hard time to bring your aircraft to such an overspeed in high level. It needs considerable pitch down plus engines at full steam to accelerate that fast (if I remember correctly we talk about a pitch down of 7.5° compared to the pitch before plus full thrust but certification pilots will sure correct me on that).
If you cruise happily along with AP/FD/ATHR on and suddenly the alarm bells go on or your plane is throwing ECAM failures at you, there is ZERO need to be ****-scared about overspeed. If you are overspeed, it won't be in any lethal way, just gently fly your plane out of it. No need to pull the stick fully backwards.
In such a situation, while you pull GENTLY out of the overspeed, AOA should be your concern, because it doesn't take a lot of degree pitch up to stall at such levels.
Once you are in the fully developed stall (high AOA due to low forward speed due to huge drag due high pitch), it takes a lot of pitch down to make your wing fly again (you basically have to pitch down nearly to your flight path vector), then a lot of time to accelerate again to a speed that supports level flight, and again a lot of time to gently change your flight path from rapid dive to level flight. I don't want to image how many thousands of feet that takes.