An interesting presentation. However, I would note that formant values coming from two different speakers are not immediately comparable due to, for example, anatomical differences, which are not so easy to disentangle from regional differences. Also, as it was mentioned in the comments, single pronunciations do not tell us much. If the same speaker said FLEECE 10 times, you are likely to find his/her formant values to show some deviation.
I found those summary maps very interesting. However, they are of necessity very broad brush. Even today, it is possible to distinguish by ear a large number of regional variations in accents that might not be obvious when looking at single pronunciations.
