Mark,
Your pictures are great. I particulary like the two nudis. I have a shot like that but without the color. (It was a dull day and I needed the 60 not the 105) However, unless your critters are dramatically smaller than the same critters that I've shot, you are not to 1:1. (Look at the exif data for focus distance)
When you get to minimum focus distance, even without a diopter, you will find that the camera has little trouble focusing. The advantage of the T/C is that it preserves working distance as you go beyond 1:1 as long as you have light on the subject.
Once you add a diopter the DOF drops to essentailly zero and any movement will break the focus lock. However, that's what you need to do to get serious magnification.
To give you an idea about the magnification of the above shot, look at the green leaf to the right, and behind, the pigmy. That is a piece of halimeda grass magnified 2.25:1, well beyond 1:1. The attached crop of the pigmy's head was done in RAW to preserve all the pixels. Ever see the crown on a White pigmy's head close up? Take a look. (FYI a White Pigmy is about 1/2 the size of a red pigmy)
My process is to get closer than minimum focus distance, have the shutter on focus priority and teh camera on "C" continuous focus with zero delay. I then slowly back away from the subject. When the subject comes in focus the camera takes the shot. I use single center spot focus.
