I fixed the broken picture links in
the earlier post - I'd forgotten to do that after I moved things around on Photobucket...
Thank you for the 3D image of the sanding block. I need to do something like that, but I need a lip for a rain gutter. I have a large plunge router and a small rotary tool and I may try to come up with a guide collar for the rotary tool to shape the edge. There needs to be enough space to get the latches in there, too. I like the idea of a slightly flexible strip of wood that can be clamped in place as a guide.