Lets see if I did this right: 9" diameter is a volume of 0.166 cubic feet, or a bouyancy of 10.33#. With two of them, that's about 20# of floatation. It seems to me you need about three times that much. Have you swamped with these?

Not that youre not on the right track, Ive thought of putting empty 2-liter bottles into the end compartments if I were going out where I thought I might get holed. But then, I just didnt go there...

: I am putting a 9" buoy in the bow and stern of my kayak for simple
: floatation and using Russ's bungie way of fastening it in tight. The loop
: on the left will be inside of an eye bolt fastened in the stern and bow
: and as you pull on the cords at the right, they become thin and allow the
: buoy to slip tight into place. Then letting go of the bungie cords swells
: them back to full dia and lock the buoy in. Thanks for the idea Russ.

: John