Jim's 2 hose clamp idea is the way to go.  It is the "gold standard" in
other industries.  Marine  standard is 2 hose clamps below the waterline, or
on engine coolant lines.  On 5/8-3/4 inch lines on vanagons I use only one.
 On larger I use 2.

As far as the junction between rubber and aluminum.  It comes under the
classification of "oxygen concentration cell corrosion".  The difference in
oxygen between the free air and just under the hose is huge. This causes a
very large voltage/corrosion.  Nothing you put on the aluminum will help,
other than a whole bunch of sacrificial zincs. Repeat, there is nothing you
can do to avoid this.

John
eastcoastvanagon.net