Another exhaust question- dimension

[trib]

Another exhaust question, but hopefully easy for all you generous responders. Does anyone have the outside dimension where the pipes exit the cowling? Reference would be from the left side of the left pipe to the right side of the right pipe (somewhere around 13" maybe). I'm curious as to how much clearance is typical from the outside of the pipe to the cowling fiberglass. Is there a generally accepted minimum distance from the pipe to the glass?

Thanks for everyone's help.