Mine all stand (but near vertical) lower limb resting on some plywood covered in carpet blocked up an inch or two off the floor.
I think the danger of leaning them is when a load of heavy junk gets leaned up against e'm. I can't really imagine that standing near vertical puts any bending stress on the bow. I have a thin lightweight chain which drapes across the front holding 'em all in place.
I think the great advantage of hanging them is that it keeps the strings in place.
I'll probably convert to hanging if I could find the space and I'd run out of other jobs to do
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Del