I'll get out tomorrow and take some measurements for you- Ill try to give a few pics as well. It was done by the previous owner to match the size of the plate itself- I don't know the measurements myself. I'll do what I can to help.
Mike

Purplefern,

I was looking for your thread all morning on you side mount plate. Is there any way that i could get the deminsions for it. I would like to build one my self. I started to make a templete from your pictures but would love to match it up to yours. Thanks!