I realize this is a much older post, but am posting anyway in case a new user has a similar problem.

The aluminum tubes in question are much bigger than the opening for the shock cord. I haven't measured them but I would say they're around 1/2 - 3/4 inch diameter. The end caps are simply plugs with a hole in them (around 1/4 inch diamter) for the shock cord. Because of this, unless you remove the end caps and use a much thicker bungee, the first method probably won't work (even though it is a brilliant thought process).

On the brighter side though, there is room to insert a slightly narrower tube, provided you can find narrower end caps to fit them. So the second method should work.

Dave H.
Prindle 18-2