Ok a lot of what's been said makes a lot of sense.
Now what is stoping one of those 55 pounders from been caught just minutes after a meal lets say a couple of 5 pound whitfish or whatever swims in its waters. There have been fish under 55 inches and over 50 lbs caught and released.
Secondly let's say the norm for maximum girth is normally 1/2 the lenght but what about those rare fish like the Williamson fish which had a much bigger girth. What if that fish lived another 5 years and reached 56-57 inches in lenght?
Even a normal fish reaching the 60x30 mark would exceed the 65 lb mark.
We know the maximum growth rate for muskie is 54 in most places with maximum giths of 27 and just over 50 lbs, nothing is proven that there isn't a few freaks out there that will grow at least an extra 10% in lenght and girth or 59.5 x 29.7 or 65 lbs.
Also different areas offer different built fish, the Thousand Island fish like the Buffalo harbour fish seam to be georging in November and their girth is mostly in a small area and not through their lenght like the other big river fish or the GBay fish.
The McNair fish was released and may still be swimming out there, maybe it will be 60 x 3? the next time it hits a net and just maybe it will make it to a scale this time around.
Do I believe there are 70 pound fish out there, maybe maybe not but there sure are fish over 65 pounds out there, which is the true world record.