Most 2S engine designs really do not care which direction it runs or how it is mounted, there have been a few exceptions through out history. 2S outboards are mounted vertically, I've seen a few ultra light drag cycles with the 2S snowmobile engines inverted and mounted to a single tubular frame member that ran from the headset / triple clamp to the rear suspension pivot. The 2S engine has nearly unlimited mounting options. I think it is short sighted / misinformed to compare it to a diesel engine of any sort. Apples and oranges, IMO. I have drawn up many a machine with the whole engine turned 180 degrees (like the Fast sleds) but run them the designed direction and reversed the rotation in the final gear reduction. Intake in front for the ram air effect and pipes straight out the back above the tunnel and below the seat. A design I've had drawn for twenty years or so is an in the driver CVT system that is fed with a belt drive straight from the crank stub to the driveshaft / CVT input (common centerlines), hollow driveshaft with the gear reduction / CVT in the center between the drivers. No heavy wide clutches and more centralized mass. Under 5 pounds rotating mass from crankshaft to drivers. That is where I foresee the greatest single evolution in snow sport technology to occur, reducing the rotating weight and the parasitic drag. While increasing the overall efficiency.