Actually, its quite possible the Fu Choy or the solid fist could be the original way we in hung sing used it. I know that Professor Lau Bun was here in the states when Chan Ngau Sing died.
anyway....in fut san they also use the closed fist in Yum and Yeung Chop Choy's like we do. So it could very well be the older way. I'm starting to think because of Tam Sam our branches started using the panther fisted chop choy's to stay current.
One story is that professor lau changed it to the solid fist (fu choy) to deal with larger, more sturdy attackers.
another perspective is that when or if you are a Hun Mun related school the closed fist in say like a yueung chop we used the closed fist because it was a secret signal for Unity inside the Hung Mun.
Hung Sing Boyz, we gottit on lock down
when he's around quick to ground and pound a clown
Bruh we thought you knew better
when it comes to head huntin, ain't no one can do it better