I like to use pink foam insulation for sanding blocks. It is light, can be sized, and shaped into any profile. A lot of times I will use folded over tape and stick a 80 or 60 grit sandpaper to the inside of a concave surface, with the abrasive side facing out. Than rub a piece of pink insulation (will be my sanding block)over the taped down sandpaper. This will give the sanding block the shape of the area that I am sanding. All that needs to be done is to remove the taped down paper and than apply the required grit to the sanding block, and a fair amount of elbow grease. I have also used the pink insulation sheets under panels that are being cut. This allows for full support of the material and free clearance for the saw blade. Tom C