Right on Doug,
I just picked up a reflecting sun screen for windshields.
Looks like it would sandwich into the middle perfectly!
Look to the ski industry...
Something that wont absorb water
something that repels it even!
That poly filler sounds good too!
Maybe nylon rain coat material for the outer coat,
& my bickie blanket for the inside !!!! night night !  kidding kidding!
when will you kids quit taking everything sooo seriously ??? :)
more me :)
John,
I am looking at designing and making up something for this use.
Please keep me in mind if you come up with more ideas along this line.

I have been thinking of using a boot on the outside only because I would
like to have access to the luggage area while in the van.
I also want rain protection and wet protection for the outside of the
canvas. The "shed" angle of covering the front luggage carrier will allow
snow and water run off.
I am thinking if a high tech fabric is used it could be stored rolled up in
the channel under the pop top outer edge. next to the canvas.

Doug