Ok thanks! I'm thinking that the netting might make it less slippery. I used mine with the Duomid as my only floor, gathered at the corners which created something of a bathtub and clipped in similar to yours using some 2.5mm shock cord. For a while I also tried it as a ground cloth for my Duplex but found it redundant... the 1oz Cuben alone suffices, and it isn't slippery. I'm sticking with my Tyvek (housewrap) bathtub for the Duomid.
Those weight numbers are right in line with what I've seen. My Tyvek bathtub is a bit over 7 oz(!), but it is perfect in every other regard and thus remains in the kit.