The ol' static balance ploy, eh?
I had been changing tires that way for years on my dirt bikes and some of my earlier road bikes. Before you pry the second side on, you can still rotate the tire on the rim pretty easily to get the balance as close as you can before you add weights, if any. I had a VW Beetle once, and the mechanic that put the tires on couldn't fit my rims on the machine, so he ended up doing them on the static balance just like that.
I haven't changed my own tires for my last three bikes. I've let the tire professionals do it with their high-speed balances. It's pretty important to have it right when your going 250kmh!