The rear rubber lip spoiler on my 84 633 is cracking rather extensively. Is there any fix short of replacement? How about some type of rubber coating I could put on it? I like the thing, it gives the M635 look (it's the same p/n spoiler), but I don't want it to crumble apart one day because of cracks the sun is causing. I'd love to coat it with some type of rubber compound, so if anyone knows of such product, or has any experience, I'd love to know. Thanks, James