http://www.youtube.com/watch?v=nLWzRD4CKTY
Here is an example of exactly what you are saying G, and Sifu Dyde is Sam Kwoks number one promoter in the UK at the moment representing Ip Ching and what they like to call 'Ip Man Wing Chun'. He moves well and is known as a decent fighter.
I find nothing wrong in using Tan Da as Steve does in the clip (around 13secs onwards) as he is doing so with courage and committment against a guy who is also 'trying' ;) but I do understand what you are saying because if you have no structure then the Tan and punch idea can simply be blown out of the water against a decent boxer.
With regards to Tan being a block or punch?? Er.... I can't be bothered! :eek: