Awesome post!! Also, regarding urethane sidewalls, we use urethane for a number of reasons. Urethane allows us to create a continuous sidewall with no seams all the way around the perimeter of the ski. With UHMW, HDPE, or ABS the sidewall meets a piece of tip space at some point to enclose the wood core, creating a weak point that can become prone to delamination. Using urethane also permits us to adjust the durometer (hardness/softness) of the sidewall to suit the ski in question. Where typical extruded sidewalls only come in one durometer, we can adjust the urethane to suit park skis and backcountry skis for either a smoother, damper ride, or ultimate toughness. Urethane is more bondable than most extruded sidewalls, so delamination from the sidwall is much less likely. Finally, using a cast polymer like urethane permits us to install the sidewall in all three dimensions, saving material and adding sidewall where you need it but allowing core to exist where sidwall is unnecessary, as you really want to have as much core as possible along the effective edge of the ski- core is lighter and damper than sidewall and most importantly it's what you'r bindings are directly attached to!