How close can I cut the front corners of my hearth pad?

[earthbelowus]

My hearth pad is basically going to be 6 foot by 4 foot, but I'd like to cut diagonal corners off the front edge so it's not an actual rectangle. How I determine how close to the stove I can come with these cuts? If the sides and front require 16 inch clearance, do I measure the same distance at a 45 degree angle from the front corners of the wood stove?

 

[begreen]

You can cut the corners as long as the 16-18" front extension equals the width of the stove and the side protection remains at 8" until past the door of the stove.