Standard frontage allotted to a single legionary?

[Q Rutilius]

It is my theory that Roman Legionaries, would have formed quickly and uniformly by simply sticking an arm out to the shoulder of the man next to him and in seconds you have formation. put your arms out in both directions, and you have 4 cubitts or about 6 feet. Both easy and fast measurements.

This is how I have always assumed that they did it. There is an imaginary 6 feet long line and the soldier stands in the middle of it. With the shield sticking out beyond the soldier's left shoulder slightly, we'd get a width of about 2'(approximately). This gives each soldier about 2' on either side that is "his space" to fight in.

Interestingly the man in the file would be only 3' behind him. Now years ago I did some modern fencing. You are taught to move back and forth - the fencing strip is long but it is narrow. Therefore, I wonder if the Roman soldier fought more in a side to side manner than the modern fencer's backwards and forwards manner. Perhaps the use of a shield inclines one to fight more side to side. Or, since it would be impossible for a file to move backwards and forwards, the soldier has to parry blows with his shield and/or move to the side, because there is no practical way to go backwards and forwards.