Am I missing something here? Wood trusses do not need to be @24" intervals, depends on the load transfers and spans. Seems like the tubing that you are going to use would be considerably heavier..who will design style, pitch..all that affect beam and load requirements. What grade and material...
Build the "damn" thing to your specifications !I served on a zoning and variance board for 10 years and you need to exercise your right to service your own needs! Experience shows that you ask for more than you would even need and through the process you have gained an area of compromse to...
Depending on the amount of run and availability of ease, a circular saw with a metal abrasive blade is my personal choice . Be aware of paint burn and kick-back.
Good Luck!