The 5 gal bottle may be to big. I have made a set of outriggers using two 2 liter bottles, works very well. I have a set that I use now that I used crab pot Buoys Spongex Green Commercial Grade Crab Pot Trap Buoys Four Pack 5" x 11" Bullet | eBay. They work the best but both sets are great to use. I use adjustable flag pole holders to mount the outriggers to the boat. I now leave the mounts set where they work the best and use quick connects to remove/install the outriggers.
Here is a pic that shows the quick connects along with the back of the kayak.