Part of the answer will depend on the condition of 3412. If it is a "project car" / "daily driver" with less than perfect stainless and fascias, a suitably sized outdoor rated cover will probably be fine, but just plan to change it every year as it will disintegrate.
If the stainless is perfect, then a two or three layer approach would be justified.
With a single layer, the movement of the cover, particularly if there is any dust or grit on the car, can add fine scratches, even with the fleece (what part of the country are you in? That's why a second inner layer helps protect it.
Mine is outside in a thunderstorm as we speak, normally under two layers - an outdoor rated one, covered, oddly enough by a soft inner one. The reason being, that the outdoor one I ended up with (with a 5 year warranty) is bright gold, so I cover it with the indoor one to reduce complaints from the neighbours
. I added a tarp this morning as I knew a really heavy storm was coming through.
It is important to remove the covers occasionally and let everything breathe