Kerf radius cuts outside or inside ?

When slicing your foam (2") , for the roof. Is it better to have the Kerf/slices on the outside of the trailer (easier to reshape) ? Or Inside the trailer ( a more solid exterior surface) and the reshaping sanding to be done on the inside of the trailer.
With the Kerf's sliced on the outside, there a wide V slices to fill with GS. With the Kerf's sliced on the inside, you'll have tight/close fitting slices....you get the idea....so what's the preferred method ?
With the Kerf's sliced on the outside, there a wide V slices to fill with GS. With the Kerf's sliced on the inside, you'll have tight/close fitting slices....you get the idea....so what's the preferred method ?
