The supplier did not volunteer this information, so I will call them tomorrow and ask if they can supply it. I will not be suprised if they can't give me an acceptable answer, as the tubing is not "precision". They sell it in 12ft "mill lengths" and have to cut it into 6ft pieces for shipping. This may also introduce some distortion in the overall straightness.
I'm sorry I can't be more helpful right now, but I will have an answer tomorrow around noon EST.
Thank you for your patience,