Hi LEW,
There are some people I know that are really good at this. They have so much experience that they can often tell within seconds if a mattress will work for someone and they just have the “feel” for it. They really are treasures and it makes the search a whole lot easier when you can connect with one of them.
But don’t get me talking about skiing … my technical expertise there is limited to say the least as you can see here 
Phoenix