G'day Mate,
I balance all my props, I'm using 16" to 18" generally, but at the moment, I'm setting up a 60 size Diablo, with OS 61FX, & about 15 mins ago I balanced the 13x6 APC that I'm running on it, the post from Aerorich is dead right.
I use a Dubro balancer, & I usually only remove a very small amount from the back of the heavy blade, until it will sit horizontal, without falling either way, then I balance the hub, this is usually the part MOST out of balance, I CA a small piece of Velcro to the light side of the hub, then CA microballons or similar on to that until it will sit anywhere I put it, without falling to either side.
An unbalanced prop &/or spinner will shake the crap out of your radio gear, & bearings, in your motor, as well as cause fuel foaming, & the bigger the prop the bigger the problem becomes.