Hm, I always thought one was okay in the rental as far as proof of insurance went, that just the rental contract was enough. I haven't ever bothered to carry info from the company policy (for biz travel) or from my own coverage (for personal travel). I'm talking as far as proof for being stopped by a cop who asks for it. If there's an actual accident or loss, you would need all the details of your coverage, sure, and I don't think it would be too difficult to get them in that event.