I have thought about PVC also as a frame and havenâ€™t tried it yet as a knock down screen for outdoor use, that could also work fine indoors.
PVC elbows for the 4 corners and 4 tees two top and tow bottom for a 16:9 screen. that will strengthen the long side of the screen and make parts shorter to fit in your car. To attach the screen how about this idea. at the fabric store they sell grommets that come in 2 pieces and you place them on each side of the material and with a special punch tool (comes with them) you smack it with a hammer and they attach. Just like the eyelets in a tarp. I have had best luck with these when I doubled over thin material. With BOC you may or may not have to double. Place these eyelets/ grommets about every foot around your fabric and then use bungee cords from top to bottom side to side to hold tension, or lace it up with some cords.
Tools required scissors, hacksaw, and hammer
Whatever you build we want pictures at this pointâ€¦.. :D