not sure if the thickness is relative to the ratio or not. I suppose in a "splitting hairs" discussion, it would be that way. If you look at your ratio cup and see the difference in 40:1 and 32:1 for 5 gallons of fuel, you'll see my point. Its not much less oil. ( maybe one ounce in 5 gallons) I think that it only makes sense to use one fuel can for both bikes. I don't think performance will be hurt or helped by changing to a happy medium. Keeping the fuel consistent will surely help tuning, but I don't think it will cure anything by itself. My understanding is that less oil is richer jetting, too. Its just not even close to going up a jet size, as far as getting a richer tune. The point was made when we all clarified richer and leaner does indeed refer to fuel to air. Oil to fuel is the oil ratio and is often mistakenly confused with the terms "rich" and "lean." Lots of debates on oil ratios' causes and affects, but i think everyone agrees to find a happy ratio with a quality oil and stick to it. If and when I have ever changed fuels, ratios or oils, I do not mix them with the old. Flush the tank and start anew, just to eliminate any adverse reactions to jetting.
I am also not an expert, but that is my opinion. Post a follow up, mr honey, so somebody in the furture has an easier decision to make, thanks.