I recently bougth a tarp bugnet combo from nemo equipment ( the nemo bug out 12x12 for reference) for a camping trip in northern canada with my toddler. i liked the product because it is very large 12x12' and we had plenty of room to play with the kid and it worked great... until it rained, they advertise the product as rain resistant but it is not. well they says that rain resistant is not meant to be waterproof when i called to complaind but this is misleading AF. i mean this tarp could have been made of untreated coton and it would not have worst.

i am sad because i realy liked the form farctor of this product and to my knoledge nobody is selling that on the market. not as large anyway.

so i im planning a diy projet to replace this one and im wondering if anyone here had advices and experience to share on doing a very large tarp like this.
i noticed that when this tarp got wet it became very hard to pitch decently (impossible in fact) and began to sag along the ridge line. is it because of the fabric? is using poly indtead of nylon would help me there.
also it became apparent that the large size of the tarp require huge tension in the tie and i started to wonder if its even a good to do this because i would end up tearing the fabric just by pitching it. mauybe pitching it from the middle instead of the corner would help that.? any advice on a fabric to use or shape to consider?
also this product is sewn with a specific triagular pattern, i figure it is for cost optimisation be maybe not. and sice im going to have to join more that 2 pieces of fabric here i wonder if there is a better way to do it?

also i realise that this will not be great in strong winds but i can live with that.

A know its a lot of question and also a bit unclear but i would like any help i can get to plan this ahead.