Great idea but worthless info until you have a specification to go against.

Use a 4’ long straight edge and it has 1/8” toe in versus a 1’ long straight edge and it has 1/8” in toe in.
That’s two different values in degrees of toe.

What’s the spec?

Now if you get zero in each case - you may be on to something. And that is assuming the ends were welded on square to the tubes.

In the OPs case, I would go with McAllister’s suggestion.
Starting from scratch - use an arbor and pucks.