just out of interest, and my skills are obviously im a long way from competeting so my opinion may not matter, but just looked at the link above, that looks pretty damn thin.
when i had my last cage i padded it with those big long, sausage like swimming floats,
Swimming floats , woggles , aid , inflatables on eBay, also, Floats Inflatables, Swimming, Sporting Goods (end time 19-Feb-08 20:55:40 GMT)
sliced down the middle and cable tied on, which give you fooking tons of padding about an inch sticking out all the way round. now obviously its not designed for that! so not likely to be FIA approved but id of thought it offers ten times the cushioning of a thin sleeve of rubber?