97
The bigger the prop the more important it is to balance it properly. In my opinion all props regarless of size should be balanced. You have the right balancer so that's a good start.
1 place the prop horizontal in your balancer and balance it tip to tip. Some guys remove material (sanding) from the rear of the blade to accomplish this and that's what I do. Once your prop will sit in this position your half way there.
2 Now let's balance the hub ... turn the prop to the 2 and 8 oclock position and you'll notice that it will turn. If it turns c/w then the bottom of the hub is heavy. If it's a large prop I have glued a piece of velcro on the light side and carefully add ca. Spin it to 10 and 4 oclock and recheck. Keep checking it this way until your prop stays and 2 and 8 and 10 and 4. If it's a small prop then add ca directly to the hub. It takes a bit of practise but you'll be surprised how vibration free you can make an airframe.
And since a picture is worth a thousand words I have attached a link to show the procedure. Follow it and you'll get results. Have fun.
http://www.Monkey.com/don3.wmv
Regards ... Frank :)