Hmmm, I think the plywood has already shown a tendency for tear outs and whilst slow and painful 80 grit sandpaper, cork block, and lots of elbow grease might be the way to go. That is how I rounded off my Swampy Tele and the current MMB4 builds. As for elbow and tummy cuts an electric sander may be better as it would cut through much quicker but would probably suggest using 120 grit due to the angles required that could be prone to massive erosion in an uneven manner if attacked too aggressively.