Here is my MYOG 1.3 oz hydration pack I made for biking. The pocket is just big enough to fit a tiny pump, wallet, keys, spoke wrench, patch kit and a few hex keys. I did the zigzag cord to carry a jacket when needed. Since I didn't use bungee cord I have a hook at the end to take up the slack. The material is 20d Momentum 90. The shoulder straps have a 2mm thin padding inside so they feel nice. Since the fabric is so thin I trimmed the corners of the platypus & added a tiny amount of insulation tape at the bottom. It looks complected but I started out making a simple square bottom stuff sack. I added the pocket, cord zigzag loops, top draw cord & shoulder straps all before sewing the bottom of the bag up. Once the bottom was sewn up I attached the bottom part of the shoulder straps. I am planning on adding sternum & waist straps. Since this is for biking the extra straps really help keep the pack in place.
The pack looks even better in person :)