I believe I read in the TCBA news that a guy used four elbows to create a 
toroid.  I don't know about the results because I never saw it.  
However, I can tell you about my toroids.  I have a 10x3 spun commercial
toroid.  It has a satin finish.  The other toroid that I have is home made.
I used some flexible aluminum dryer duct (3") and formed a ring.
Then I took some aluminum solder that I got at a welding supply shop and 
soldered a disk of aluminum into the middle of the ring. Actually the disk
was a duct cap that was 6" in diameter with a lip of about 1/2" inches.
In cross section it looked like: |__________| .  I covered half of it with
aluminum duct tape and left the other half in its uncovered form.  This
uncovered part has radial corrugations, much like the radial belts of a
tire.  When I fired the coil up, I didn't notice much if any difference 
between the taped or bare part of the home made toroid, nor did I notice
any difference between the two toroids.  I suppose I could have measured
the total spark length, but I didn't have time, so I just relied on my 
eyes and memory (always risky!).  
The most notable thing is that the surface of the toroid, while free from
points, was not smooth.