This is not an advice; it's only my experience. I think you can remember my setup.
First, the base plate. I guess you are going to use the tracker plates, wich makes things easier. As you see, the center of them is the middle between the holes for the base of the trucks.
Second: placing the boot in the plate. In my former pair of rollerskates, the wider part of the boot (you know I use ice hockey boots) was centered in the wider part of the plate. It worked right. I set up my actual pair differently (looking for a better way of setting up them). I drow a line in the center of the boot and aligned it with the center line of the plate. As I did it I could see that the fore part of the boot was "looking" a little bit outside (the left toe was turned to the left and the right toe, to the right). I trusted logic and made the marks in the sole of the boot through the trucks base holes. Then I drilled the boot. The result was that since that I skate with my toes lookig a litlle bit outside. It's a little strange and it doesn't feel as confortable as when I centered the boot sole in the center of the contour of the wider part of the plate. Anyway, I can skate with no problems at all.
Third. It's better if you can put all the screws of the trucks bases into the boot. Some of my friends leave the two that correspond the heel without beein gfixed to the boot. I think this gives you less "feeling" of where are you rolling and I also think that it can help to break the boot sole quicker than usual.
Fourth: At the heel, I use to move forward the end of the truck base 2 or 3 mm from the end of the boot sole. If the plate shows too much at the toes, then I cut it and protect it with a thick bumper made of tape.
I send you by mail hi res photos of the set up.
I'm sorry for my English. It's difficult to explain!!