Back in the day, when all I rode were tubies, I would fold them so that the valve was in the to of the fold with glue touching glue. Then I would fold them in half, fold them in half again, stick it in an old sock & strap it to the inderside of the seat with an old toe strap. That worked for me for many years; even living in Colorado Springs at 6000 feet.
Thank you,
David