I have just bought a 3100mm x 610mm roll of A90 Blue 5mm Kaylan which according to everyone that sells Kaylan Mudflaps, is the WRC Rally Spec Mudflap Material.
I have been unable to find replacement full size mudflaps as fitted to the RA anywhere, so intend removing the "Standard Red" ones to use as a template (keeping the original brackets), and then making my own.
If anyone wants to buy some of this material from me, please let me know.