Duomid inner floor material?

I have a Duomid arriving soon and am looking at floor linings, I'll mainly be using a bivy bag with it although I have the inner net also.
I was thinking of using Tyvek as I hear it is hard wearing and light, but I'm wondering if it has any water resistance at all and whether that is something that would be necessary for this set up?
Otherwise I'm open to suggestions of any other light weight possibilities?
Thanks.
I was thinking of using Tyvek as I hear it is hard wearing and light, but I'm wondering if it has any water resistance at all and whether that is something that would be necessary for this set up?
Otherwise I'm open to suggestions of any other light weight possibilities?
Thanks.