I do not know much about the 6th Panchen Lama though he is mentioned in
http://www.dorjeshugden.com/great-masters/recent-masters/9th-panchen-lama/ There is some detail in the context of his strong and close relationship with Emperor Qian Long as the Emperor gifted him with a painting, a gold seal of authority and a golden sheet of confirmation among other affirmations. (
http://www.dorjeshugden.com/forum/index.php?topic=2833.0).
However, it seems logical that the 6th Panchen Lama was a Dorje Shugden practitioner since it is prevalent throughout the lineage.
Here the 11th Panchen Lama pays respect to his predecessor before receiving Tibetan Buddhism scholars. I wonder if these scholars are Dorje Shugden practitioners too.
Panchen Lama receives homage from Tibetan Buddhism scholars in Beijinghttp://www.ecns.cn/visual/hd/2014/05-19/39123.shtml2014-05-19 08:55Xinhua Web Editor:Wang Yuxia
The 11th Panchen Lama Bainqen Erdini Qoigyijabu pays respects to the cenotaph of the 6th Panchen Lama before he receives homage from Tibetan Buddhism scholars at the High-level Tibetan Buddhism College of China, in Beijing, China, May 18, 2014. These scholars include monks who were offered the "Tho Ram Pa" degree (one of the highest academic degrees in Tibetan Buddhism) and the "Nzhing Ram Pa" degree (an intermediate academic degree in Tibetan Buddhism) and judges of the "Tho Ram Pa" degree. The degree-offering ceremony is held at the college on Sunday. (Xinhua/Xie Huanchi)