http://www.chiefdelphi.com/forums/pi...&quiet=Verbose
Our arm last year worked great, and kind of matches your layout, but the lower section pivots from the bottom. I don't think you could use this wide setup at the height you want within the weight limit though. But you might want to look at the mechanisms used. Particularly the window motors for the upper arm. We used 6:1 for the ball plus the arm weight and it worked easy, but you'd need a little more reduction for a tetra. Unfortunately our lower arm section used 2 globes, but this year they only gave 1. You could possibly combine the Van and globe for the lower arm section. They both operate close the the same rpm (75-80)
Go to our website below if you want to see some video of it in action.