Bona,
I think you will be just fine if you stick with the paper plate sized kill zone!
However, The MOST important thing to remember is that Moose are a BIG animal!!!!! Range estimation can REALLY be a big problem... The average size Moose is about the size of a Holstien,except about 6 feet tall at the top of his back. I would suggest if you have a farmer around that won't mind you wandering around in his pasture, get out there amongst the cows and practice judging how far away from you they are. It doesn't make up for the height,but it will give you an idea of the body size.
GOOD LUCK!!!!! May the Great Spirit guide your arrow!!!