My sight glass is currently poly, but I've been thinking about something like this for a future glass upgrade. Rather than starting with a tube, my idea was to start with a flat sheet, then bend it into a C-channel shape and weld directly to the eye bolt at the top. I hadn't decided how to mount at the bottom, but a similar method should work. I don't think you'd want to weld directly to the fitting nut on the bottom, but could weld to a SS washer that would then fit between the fitting and nut. It seems like this would be less work and you'd have those nice clean edges.