I mounted mine so the garage door just missed it when it closed, and in the middle of the opening. I wouldn't mount it directly in the middle unless your garage is huge. You might have to make some bends out at the end of the tube and still have 18' coming out the other end of the bender. I just have my door open when i bend anything.
My cage was the first thing i made after i bent a 90 to use as a pattern for layout.
Tony