I ordered liquid rubber to add a few layers through several days. This chemical should bind with internal layer of fabrics that isn’t waterproof but is very strong instead. Inner layer prevent you from damages of any forces when external is just waterproof. When removing collar I did not avoid refraction of two layers in some places and I realized glue binding internal and external layer was revealing significant signs of being outdated. It’s physical characteristics changed that it is no longer a glue but kind of powder. So some parts need to reconstruct from scratch layer by layer to make it water proof and strong enough to glue latex or rubber to it after a few days of adding liquid rubber layers. It is a very time consuming work and needs some tests and experiments after that. I ordered also glue Aqua Seal from the USA that may complement my own selection of glues. I have many types of them. I like brand Technicol, sometimes I use cyanoacrylate glues but for different purposes, many types of classical rubber cements like one even ordered from the USA last autumn to fix some latex fabrics. I have even one glue designed for fixing transmission belts in factories! A huge range of products and when you know it will be used close to your chest, neck etc. it must be chemically neutral after (dis)solvent evaporate completely. No mater what you use I should become neutral after a few days – chemically, biologically – it should create new layer, clean and smooth new surface.