Using Best brand rear main seal 3878 - new repro

Courtesy Man

Just received the rear main seal for Hudson Big Six - anyone tried this? It is a narrow rubber half circular seal. The original is much wider and sits next to a deep groove that accepts the other cloth and twine seal. Lip on new rubber seal seems much too narrow to work and in the instructions no mention of the twine seal - only description of using the included mop twine on the vertical grooves of the main bearings. Anyone familiar with this - is it a waste of $60? Thanks Gert