I think rain is likely, I use some 2" foam pipe insulation that is
split lengthwise, place it over the spoilers, then use a bungey on the
spoiler handle to pull the spoilers down against the foam. The foam
seals the gap.

Someone mentioned boards with insulation or aluminum to spoil the
lift. I'm a bit worried about damage to the surfaces. I
was thinking that some foam "hollow column shape" wrapping,
cut in half and put along the leading edge, might work for
this. Has anyone tried any of these three (boards, aluminum,
leading edge)?