Hi
CNC Kitchen just released a video where Stefan explains how he implemented "Gradient Infill". Unfortunetely no slicer implements it yet. This would be a really cool feature (and S3d would be the first to implement it).
He basically varies the flowrate from 25% to 300% depending on the distance to the outer perimeters...
The results are impressive.
Link to the video: https://www.youtube.com/watch?v=hq53gsYREHU