To answer the question of the thread is all but impossible. Let me make a comparison and we will use another animal as an example. Let's use...humans as a comparison since we are animals as well. How many dead squid do you suppose Mr. O'Shea and all his colleagues have studied that have washed ashore over the world's oceans since modern science came about? A few hundred maybe I would guess, correct me if I am wrong. To try and use those measured example as a size range is logical but to try and use them as a known maximum size of the species is utter folly.
Let's say you are an alien race and come to Earth to study humans. part of you mission for the biology of mankind is to dig up a couple hundred random dead bodies from a public cemetery and measure them and perhaps catch a few live examples. What do you think the size range of a sampling of a couple hundred human carcasses would be? here are some stats for you. "According to the Height Analyzer, the percentage of men taller than 6'4" is 0.5%"
So what is the tallest person you are likely to get in that sampling? What are the chances you would get someone of Shaquille O'Neal's size & foot 2 inches high? better than winning 2 lotteries in a row I bet. Here are the stats: "According to a scientific study there are 3 people 7 feet or taller for every 1 million people, so there are roughly 20,000 people over 7 feet tall." That is in the World
Plus, what is the chances you would get Leonid Ivanovych Stadnyk who is 8 feet 5 inches tall 9the World's tallest living man)?
http://www.mahalo.com/leonid-stadnyk
What would be the chances you would dig up Robert Wadlow formerly of Alton IL. who was 8 foot 11 inches tall?
Robert Wadlow - Wikipedia
There is also an unverified account of a man who lived in the Arabian Peninsula long ago, Gabara, the Arabian giant, whom was 9 feet 9 inches tall.
Apply the same statistics and ratios to giant squids. I have a very eclectic mix of interests, i always look for the biggest, meanest, heaviest of animals and this manner of think can be applied to any animal, all have genetic freaks far a larger than the normal size range (for example a 902 pound Black bear or a 276pound Mountain lion or a 2,000 pound pig). All predators have their own legends of ancient giants terrorizing the community like Big Jim the rattle snake in Frontier time Illinois and Indiana or the giant 400+ pound snapping turtle known as the beast of Busco in the early part of the 19th century in Indiana.