spreaders, shrouds, and trigonometry

[art heyman]

If the spreader should bisect the shroud at equal angles (above and below) , why do I see so many spreaders perpendicular to the mast ?

Obviously the spreaders need to be angled up; (?) otherwise the angle the spreader makes with the shroud will be about 90 degrees below and significantly less above, as it angles up to the mast top ( leading to forces other than direct compression on the spreader as the boat heels )

As I calculate an appropriate spreader angle for my own boat (mast height 35 feet, from spreader to mast top 210 inches, spreader length 41 inches) I get a 5 degree elevation, about 3 and a half inches above the horizontal at the spreader tip. (My spreaders are in the plane of the mast, they don't angle aft or forward; the only angle I'm concerned with is that of up or down)

I was about to set it up like this,with a distinct upward angle, then wandered around some yards looking ( in some cases at very expensive boats of good pedigree ) and saw that perhaps 8 out of 10 larger ( 30 feet and up) boats had spreaders parallel to the deck

What am I missing ?