As with most "critical" decisions, there's no easy answer to the
questions raised. I've built a bunch of solo wing riggers and decided
on high-density closed-cell foam because of the higher friction: it
grips the wingtip and doesn't slide around as much...until it dries
out, that is. I discovered that leaving it out in the sun hastens this
process so now I put the device back in the trailer after I rig. The
closed cell foam doesn't seem to absorb or hold much moisture although
any moisture does reduce the coefficient of friction. The high-density
stuff compresses just enough to allow clamping the wingtip firmly
without risking dimpling the skin. With felt, you need a much closer
fit or some other way of allowing for positioning the gripping part of
the saddle in different places (inboard/outbaord on left or right
wingtips, for example). The open cell foam that came with my wing
wheel was the worst. It holds moisture, degrades, and stained the gel
coat, although it will happily install nearly anywhere in the first
few meters of either left or right wing.

Felt doesn't degrade nearly as much as foam but it doesn't compress
and absorb shock as well and it does hold moisture. It also packs down
over time under constant load (e.g., in the leading edge of a wing
support cradle).

I tried indoor/outdoor carpeting and traditional indoor carpet as
well. The indoor/outdoor stuff tended to separate from the foam
backing after a few years. And it seemed more difficult to fix all
types of carpeting in place with adhesive; the edges kept coming loose
and flopping up. My sense is that carpet is probably the worst in
terms of holding grit although I have no way of proving it. Marine
carpet might be better.

Contact cement is quick when you have easy access; when it touches,
it's done. Caulk or adhesive of various types gives you some time to
move things around but, of course, you have to keep things fixed
during set up. One suggestion: give some thought to how difficult it
will be to remove the old adhesive when it comes time to replace the
padding.

Chip Bearden
ASW 24 "JB"
USA