Lower cylinder wall temps would increase the viscosity of the oil on the walls, which might allow the oil concentration to be a bit lower to have the same effect.

But OTOH I'm doubting that would be a big difference. Cylinder wall and pistion temps are a lot higher in air cooled engines than outboards and that is one of the key differences between the oils that are rated for air cooled and water cooled applications. So air cooled oils have more bright stock and therefore hold viscosity to a higher temp so that they don't stick rings of have scuffing near the exhaust ports at those higher temps. They are like grapefruit and oranges, they are both a bit different, but they are both citrus and there's a lot of similarity too.

I'd still figure that the percentages where best power is attained is probably in the same general area, not up at 32:1 and certainly not at 50:1, and probably not down at 10:1 either. If the manufacturer told Tim they ran power and durability at 16:1 that was from their experience, so we have 2 data points in the same vicinity. Like I said, every engine is going to be a bit different. Some might like a bit more oil to seal, others might need a bit less, and it's going to change with viscosity of the oil you are using, the temperatures you are running, the clearances of that specific engine... It goes on an on.

We aren't trying to nail a specific number for any specific or all engines, I just want to get in the ball park and find home plate, not specific blade of grass.