If you are making calls for yourself, it really makes no difference what tension others put in their calls,...you want to make calls that work best for you. The best thing you can do is experiment with different latex tensions and call designs until you hit on what works.
If you are making calls to give or sell to others, you have no idea what will work best for them, either, unless you sit down "one on one" with them and actually figure it out through experimentation.
Another factor: I have used lots of different calls from different makers, including my own, and I have yet to find a call maker that can make a mouth call that sounds exactly the same call to call. The minute variables in the latex itself,...and in the call-making process,....make it impossible to achieve exact consistency in calls. Combine that with the fact that every single mouth call user has some variation in technique and ability, and it is clear that trying to find an exact tension for latex stretch for each individual call user, and then making the exact same call every time, is a pipe dream.
My opinion is that anybody that wants to be the best mouth call user they can possibly be must start making their own calls and go through the learning process of what will work best for them personally. Of course, most mouth call users don't really care about whether they are great callers or not,...they just want to get to the stage where they can call turkeys,...and the fact is that the turkeys just aren't that particular.