mommamia22 u r welcome.
cherrybim Actually, the thickness of the rolled up tarp is already more than a tefach
I believe the poskim bring a gemara against this since a roll is evidence that it is not an existing tent and are machmir but a partially unrolled is ok, if I have a chance to post the source later I will, if not u may want to check in MB chelek 3 simanim on ohel and binyan.