We all get there in the end in this case, but it was the use of the term, "rule of thumb" which isn't one i tend to use or certainly one I would advise others to use when there are proven ways of reaching a solution.
Ever wondered how we got the phrase? Well;
A rule of thumb is something that works 80% of the time. 1 out of 5 times it is wrong, the thumb is one of 5 fingers,
hence the term "rule of thumb"