Tent footprint: exterior hem or not?

Hello Making Friends

I am making a footprint for a tent from tyvek: should I hem the exterior so that the fabric folds over from the top side and is sewn (or taped) to the underside? What about adding gromets?

I am thinking that the hem would keep ground water from seeping between the tent and foot print if it were to rain.

I am also thinking this is too much work for very little benefit, and an unfinished edge is simple, easier, and just as durable (this is freaking House wrap).

Thoughts?