Cutout Placement help

-- I am wanting to add cutouts into the X-pipe before I permanently put in place. My question is how do I know where would be the most effective place to weld them into place. Also do they need to point down or can they be mounted towards the sides? --
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On My 500 inch 68 Dart, I put them ahead of the X-pipe - no special reason. -- I pointed them slightly down. My thinking, on that, was to carry the fumes away better.