Is it feasible to practice hard pen calligraphy at the age of forty?

It is feasible. I suggest you start with soft brushwork and cultivate your calligraphy accomplishment. Now all universities offer calligraphy majors. At present, all colleges and universities (***63 colleges and universities) in China enroll calligraphy majors, and Peking University, China Renmin University, Zhejiang University, Nankai University, Sichuan University, Shandong University, Southeast University, Suzhou University and other Chu Yuntang calligraphy college entrance examination training courses will answer your questions.