My cowl cover is much like a down jacket, but it’s polyfiber insulation. When it’s not winter, it’s stuffed into a large garbage bag. I could fold and squash it down much smaller, probably less than half the size, if needed. Fortunately, I have a cherokee with plenty of baggage room as well as the back seat. Another benefit, is that the cover is bright orange, so it works both for emergency blanket as well as signaling.
Hm, might be an interesting project this weekend, to see how small I can squash it and how much space it really takes up.