This does not matter when it comes to YS engines. They can be run at any attitude, from any angle and as far from the fuel tank as needed You will still need to be vigilant when setting the low-end but in my opinion the YS is the pinnacle of 4 strokes.

I have owned the YS-63 and it was a wonderful engine! Saito's are awesome but I'd take the YS-63 over a Saito-72 or 82 any day