With scissors and cutter knife I remove the OUTER little lip completely (what is left of it anyway), and on the INNER lip I leave just sufficient rubber to attach the new strip on. You can really feel - when you cut the old rubber edge off, that this is utterly dry and brittle rubber, which the inner remainder is still soft rubber. Obviously the old rubber remains need to be cleaned (with isopropanol alcohol or wax & grease remover) before attaching the new strips. Cutting the old rubber is actu