Hi GrahamB,
Unfortunately I'm not his student, as I live in Italy and him in New Zeland..
But both my Chen Tai Chi masters (George Xu and Flavio Daniele) both Tuky Lum learned from master Ma Hong.
Tuky is a very kind person and sometimes we exchanged emails.
I think that when you practise two arts it's difficult to keep them well separated because you develop your own way of movement and you have only one body!
Maybe he founds useful aspects in both arts.
Regarding which part of the body should initiate the movement I've heard two versions: 1) the dantien initiates the movement and 2) the feet start the movement and the dantien acts to transmit the force to the remaining parts of the body.
I tend to move according to the second method.
I'm sure that if you will try to contact master Tuky, maybe on
http://groups.yahoo.com/group/taichichen, he will be happy to reply.
Bye,
.-)