Irasman,almost no one in this forum flames people as a general rule. If you say something that someone disagrees with they usually just post why they think you may be wrong in what you say, and in most cases with tact. They also supply a reason or fact behind why they think you might be wrong. All of us are here because we want answers to questions we can't solve. One of us is bound to know more than an other about one thing. That's why the forums work so well, we try to get along and not be pre-madonas or showoffs.
I happen to agree with what you say, if you design things correctly, you should get a high tolerance in your network. So 60-80% sounds reality based to me as long as you have all your stuff squared away. Besides, isn't that what QoS is all about getting the most out of you available bandwidth.