I was furnished a handbook of engineering data to work with and help with calculations. It gives drawbar pulling forces required for different types of soils vs depth, and width of cut.
To pull a 12yd scraper when full just before stopping the cut requires just over 40K of drawbar pulling force on the horizontal plane and this is where pulling unit weight and traction is a large player. I have published data on the tractor. The target towing speed of a production scraper in action is between 4.5, and 6.0mph but I don't know if this speed is during the cut, or transport to dump area? To attain 42K of drawbar power my tractor is down to .56mph in low gear. Based on this information, it is why the tractor is deemed unsuitable for the 12yd scraper. Of course any manufacturer data is based upon ideal conditions, perfect, or new equipment without wear, etc.
All thing equal, a 10yd scraper would require less power from the tractor being narrower in the cut width and less weight in the bowl. This data of course is variable upon scraper design. However, a 10yd scraper may still be too large given the target cutting speed desired for this tractor. Being that I'm not looking for production speeds there are tolerances available and I have yet to evaluate this scenario.