I see, so by changing the characteristic curve, you appear to change contrast without actually doing so. That changing your agitation actually changes the steepness of the curve, rather than the limits of the values. I hope I re-stated that correctly. My main question is the will change in developer with the same agitation lead to blocked highlights? That's probably the way I should have phrased the original question. It also appears that the answers given here generally agree that trying my current method is the best starting point.
I have tried different agitations, primarily for increasing or decreasing the highlights without a great change in time. I hope this makes sense, as I've only been doing my own development for about 11 months, and seem to have found what works well for me.
Thank you for your answer and the help. I really appreciate it from everyone!