Dean, I really take my time on the handle wraps.
The following is how I lay one out:
Decide how long you want your grip to be.
With a ruler draw a straight line that length on a piece of paper.
Then with a string take several measurements starting at the top and working your way down. I measure so that there is an 1/8" or so gap to the front to allow for stretching of the grip material. Transfer these measurement working down the centerline of your first line depicting the grip length. Of course these circumference lines will be placed on your grip length line at their midpoints. Hope that made sense.
Then connect the lines with whatever natural curve makes sense.
I then cut the paper template out and try it on the bow. I usually fold it along the centerline prior to cutting it out so both edges where the front lacing will be are matched.
Tweak the template if needed, then use it to lay out your grip material.
I don't like a blocky style grip, want one that is comfortable to my hand which means it changes circumference quite a bit from the top of the grip to the bottom. The instructions above help get it pretty close the first time you cut out your material.
Hope that helps!