LOL, Tony.
Nope - no stainless, all Aluminum. The internal piece cost me $300, the tabernacle only $120. I could have probably gotten the internal piece a bit cheaper, but made the mistake of mentioning that that amount was the most I wanted to pay...
Don't tell the fox where you hid yer chickens, ya know?
Thereafter ever aware of those consequences, I drove a harder bargain for the tabernacle.
There is a flat bar on top of the internal structure. I figured it would add more bearing surface, and be easier to 'mate' to the overhead that way instead of to the tubing.