Your tarp turned out really nice looking. I like that very much. Are the ends straight if you lay the whole thing flat, or angled away from the connection point?
I actually did put a reinforcing stripe of clear duck tape on each corner, but not on the edges, in the direction of the tension. I also had cut the strips to half width to save weight. Obviously, that wasn't enough reinforcement. I think I used a sub-par brand of tape as well, not 3M. If I make a polycryo one, I'll definitely reinforce the edges, but I don't think I'm going to mess with grommets. There's too many reports that they eventually pull out. That happens even on store bought tarps.
The tent I made a year or so ago was made of those SOL Emergency Blankets, but I haven't slept in it even one night. Shame too, because it's light, and roomy. and packs small, plus I've probably sunk well over $40 into materials. I'd had big plans to make that my main shelter, but my wife can't stand the sight of the bright orange plastic. I had to stop setting it up for testing, so I never got everything tweaked just right. I still have it. I'm still trying to make up my mind what to do with it - cut it up for parts (metalized plastic, no-see-um, zipper) or try to find someone who wants it as-is. More later, I've got to go now.
The journey is more important than the destination.