Thanks for the advice. I took out my 300 F4 for the first time today. It's definitely the heaviest lens I've ever used. I shot three hours without a tripod. Results weren't too bad, but I will most likely start using a tripod 75% of the time. Because most of my macro work is almost entirely butterflies, my 300 F4 won't see too much macro use, as the insects I photograph require me to be pretty mobile. But I'm sure that times will come up when I'm shooting birds, and a butterfly will come out of nowhere. At that moment I'll remember what you said, and give it a shot.