Here is something to consider: It is the shape of the tire, most front tires are more raised in the center of the tread, it helps the bike turn-in easier and balance at really slow speeds. Many rear tires have a flatter center, you may want to select the one that has a more rounded shape, more triangulated profile for steering control. Just a thought...
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You can use plastic air soft BB's to balance the tires, they work as well as anything, they are cheap and don't deteriorate over time or harm the inside of the tire.
I can hear them inside the tire if I roll the wheel and stop it fast while the wheel is off the bike, you can not hear them while on the bike. (i can't)
You can not install them through the valve stem but it's easy to break the tire bead and install them at any time and really easy during a tire change.