You guys are a great bunch! Thanks to everybody for the advice, tips and sharing of your experience.
I talked to the instructor and told him that if I was unable to get stable on both knees, I would try the one knee approach. He said it didn't matter because we were about to perform the BCD removal and replacement skill and that requires that I go to one knee anyway.
So, tried both knees again but still having the same problem, body tilts forward, blah, blah, blah... Went to one knee and everything worked out right. Performed the complete mask removal, BCD removal/replacement, weight belt removal without any problems.
Thanks again for the replies. I really appreciate it.
Anytime you're in Hong Kong, look me up and I'll take you out for Dim Sum.