Very impressive start with the bellows.
In some of my trials I found using a bar code label helped a lot with focusing. With the very limited DOF at these magnifications point of focus selection needs some thought on anything but flat objects.
Harry ( wolfie ) has been playing around with a program that looks to be very interesting in this field.
Question - does your camera have a ' mirror anti shock ' mode in the menu. That is what I use with the D100.
Don