Puppet Man,
This magnificent new medium we have (the Internet) for communicating with people all over the world also has its detractors. Sometimes we write things in posts that do not come across well, even though we could say the same things in conversation with a friend with total immunity. I'm sure I should be much more careful about how I say (write) what I say (write).
Thank you for your most helpful posts. I did not read over your recent post without thinking about it, as you suggested I might have done.
When I wrote that I was not convinced that you can make the 'F' sound by making the 'th' sound, perhaps what I should have written is that "I am not convinced that I personally can do it, but perhaps I can if I practice long enough." I probably spoke (wrote) too soon.
As to whether or not I have enough time to do this, well I'll just have to try it and find out.
You asked if I had practiced what you explained. Yes, I have, but not nearly enough.
Last night I watched the movie "Dummy" for the second time, but this time with much greater interest. I found myself going back over and over again to relisten to something the dummy said. In one case the dummy said "Steven." It really sounded like "Steven" with a 'V', but I did not think that the vent could actually say the 'V'. On about the fourth listening, I heard something more like "SteTHen." It seems that what I had been hearing as "SteVen" all along was really "SteTHen," but that my mind was changing it to "Steven" because that's what I wanted to hear.
The question that raises for me is this:
Can one really learn actually to make the so-called impossible sounds without moving his lips, or does he simply learn to make very similar sounds in such a convincing way as to create an "auditory illusion?"
LATE BREAKING NEWS: I just received an email from an important person in Nigeria who wants to share 20% of a 35-million dollar fortune with me. All I have to do is to provide my bank account information! It looks like my ship has finally come in. Now I can buy the Maher ventriloquism course and have lots of time to practice.

Thanks again P.M.