Wayne, I hear you, it's a guessing game, and it's been this way for decades. You have to be hands on, experiement with the range, it's at best, we can whittle down to some degree of what is appropriate for scale to use application. Meanwhile, I have a loyal and just good person customer deciding to stick gear that can handle 4-5 pounds of flight, onto my Extra which is designed for the 250 gram, back yard flyers...
I do like Emax dealing with them directly, they are a class act, us in the west need to fill in the gaps I suppose in their case, even basic stuff along what their gear should be doing, powering, all that... I am impressed too with the quality. I see this lonely little motor, qty 1, and see it's specs and know it's just fine for these 250 gram scale of models.
I have recommendations, etc. on and on, but it's not some numbers the manufacturers or others put out, it's hands on and taking them myselves. I wish I had that little motor in my hands right now, I would give you better input upon it's capacity and put it into some degree of the best spot you can use it for.