One last thing: You can also purchase a raw mast extrusion. or a used mast. This will allow you to have a build it rail for your trampoline.
I have two H17 mast extrusions that would be suitable for this purpose.
One is punctured right below the sail track. The other is bent about 3' from the end of the extrusion. Either one would give you more than enough for two 10' beams.
