30" x 72" raised flue pan build

[maple maine]

I am having the pan built in the machine shop where i work
Questions
from what i read should the flues be 1"X7" set 1 inch apart?
30 " pan what should be set back front edge? (how many flues)
what should the setback be for the front and back of pan? (how long should flues be)
any thoughts and ideas welcome

[maple flats]

My flues leave about a 2" channel at each end. The flues have about 5/8" between them on the sap side and about 1.25" between them on the underside. My pans were made by Thor in Quebec.