I thought this would be a hassel to do, but it only took about and hour total. I pretty much just marked where i wanted the bump, and how far down i wanted to take the seat down and crafted away from there. I started out taking the steeper depth cut with my hack saw and kind of worked a little radius in the foam as i cut away. then i made the shallower cut to meet up with the steep cut i did earlier. once the cut met up, i could remove the triangle like foam piece out and i created my bump base to work with. i bought a little sandpaper wheel for my air grinder the sculpt the bump's curvature, then used regular (120&180 grit i belive) sandpaper to fade in the rest. coarser grit sand paper wouldve worked better to rough it out, but 120 grit was fine for me. I did finish up some of the edges a little better after the foam pics were taken. i think it turned out pretty rad.