ATM Over arm for grinding machine

[JAMccaf4u@aol.com]

Hi to all,
I am building my grinding machine and am to the point where I am about to 
build the over arm and I wanted to know what type of designs are available. I 
have seen both the single and double arm style's. which is preferred. My 
turntable is 17" dia. Also, I need to know how much swing I should put into 
the arm. In other words do I want the arm to swing center over the edge or 
less. I need help in this area. If any of you have web pages that show this 
please send your URL. My machine is based from the Tom Waineo style. I am 
using two motors.
Thanks Joe