I understand you want the issue in an effort to dismiss or perhaps discredit the text...however, we do have evidence of how long the cubit was. Suffice to say it was of a sufficient size to accommodate the animals and Noah's family.
Had you read the entire thread, you would have seen that my issue is with text that reads "exactly 300 cubits". If one wants to write a scientific-like article it is unwise to claim exact compliance with a unit of measure that varies according to individual people. I know of no credible association of anybody's cubit to modern measurement systems. The claim that some Egyptian unit is accurately known is not well substantiated and the notion that Noah used the Egyptian unit is preposterous.
The author would seem more credible if he used language that took the lack of precision of a cubit into account.