Mark, the ribbed belts usually are installed on a serpentine path, but "serpentine" just refers to the path, not the belt itself. That's usually done to accommodate the placement of "stuff" on engines that have to fit in engine bays, or where there's one shaft or pulley "in there" as opposed to "out here".
"Any double belt or straight belt is going to load a small engine bearing in a detrimental way." Not really. The bearing has nothing to do with it, you could install a 1/2" v-belt on a 2" wide pulley and the pulley and bearing wouldn't know or care if it was a v-belt or a ribbed one. The problem is, when you use double belts inevitably one stretches more than the other (they used to be sold in matched pairs for that reason) and winds up carrying the whole load and snapping. And if you just used onebelt, there was never enough surface contact between the belt and the pulley so the belt starts slipping, somewhere around 80-100hp, and then that belt starts to come apart. Or some gorilla overtightens it, and that can kill any pulley regardless of the belt type. And usually kills either the alternator bearing, or the water
pump, in car and truck engines. (They're usually on the same belt.)
The automakers *may* have had a good idea in switching to serpentine ribbed belts, because the belt tensioner is usually what pushes the belt "in" so much that the path becomes serpentine. And while belt tensioners often wind
up failing and creating a maintenance
issue, they also ensure the belt is properly tensioned (when they work) because no mechanic
ever got fired for not using a belt tension gauge, despite "every" factory manual telling them to use it every time they touch a belt.
engines? Well, with so many 30 year old boats around...<G>...we're the only folks left on the planet who still use v-belts. Except for British Sports Car enthusiasts, of course.