Somebody should be along to answer your theory query, but note that all pipes get hot and your boots may always be at risk. Some boots and some feet are more at risk than others. You've got to experiment a little there. Most aftermarket pipes are slimmer than the stock can's, which may be enough to avoid your soles. Melting pillions soles & heels won't show up so badly on something like the Agostini black muffler. Ceramic coating the pipes not only enables them to cool very quickly, but also easier to remove any melted gunk. There are likely to be be solutions, which ones work for you is a matter of experimentation.
