Walmart "Outdoor Fabric" for MYOG Daypack?

Hi Everyone,
I'm in need of a daypack or overnight pack that'll double as a pack for carrying my books to school on my bike.
Last time I was looking at fabric at Walmart, I saw they had a material labeled "outdoor material". I believe it's pro-tuff PVC coated polyester, 25% polyester, 75% PVC. It weighs 20 ounces per yard, but I'm not worried about weight for a daypack. I know Xpac is less than half the weight, but is around $17/yard plus shipping and there's also Cordura 1000 for around $11/yard. I think the pro-tuff was $5/yard.. I was just wondering if anyone had used this before and how it held up?
Thank you!
Scott

Edit: I just had an idea to use the Walmart backpacking tarp to make a pack. It would be much lighter than the pro-tuff fabric. Would this be strong enough for a pack?

Not for carrying books in.

"a daypack or overnight pack" - pick one. Overnight packs have different needs and therefore different features.

You *could* use the same pack for all three tasks, but you're going to find it will only work well for one.

Honestly, buy a book bag...from Walmart. I use one (jansport, i think, recycled from my kids school stuff), striped down for day hiking, motorcycling, bicycling, etc. You can remove a lot of weight by cutting out dividers, and all the extra bling you won't use. The material is ballistic nylon and made for rough use. You can't make it as cheap as you can buy it. Since school is starting, you'll find them on sale all over the place. And...properly gutted, you can make a dandy day ruck sack from a book bag and might even get a couple nights out of it.

Thank for the advice everyone.
Maybe I'll make pack just for cycling. I was using a regular backpack, but I'm riding 40-50 miles a day and it's tough on my shoulders. You wouldn't think it would be so bad, since you're hunched over, so more of the weight is on your back than your shoulders, but it is. I was hoping I could make something with wider more comfortable straps and maybe a hip strap. I also need quite a bit of space for my laptop, books, change of shoes, water, lunch and change of clothes.
With my old bike I had a rack and panniers, but that isn't an option with a carbon fiber frame..
I might still try making an overnight pack that I can also use for school. I'll probably use the "outdoor fabric" unless anyone has had any bad experiences with it.

Get a rack that attaches to the seat post only. Then you can put the heavy books on that.