I would not miss the chance to study with Guo Laoshi---he is a no BS guy and knows both Chinese culture and Western Science well---he is one of the best baji/pigua practitioners I have ever seen or met.
If he still teaches Chen's taijiquan, you can't go wrong and he also knows Liu Yun Qiao's bagua at a very deep level.
He is the real deal and from what I understand, his son is also top notch!
"Its better to build bridges rather than dig holes but occasionally you have to dig a few holes to build the foundation of a strong bridge."
"Traditional Northern Chinese Martial Arts are all Sons of the Same Mother," Liu Yun Qiao