Just for laughs I jumped into AutoCad (easier than math in this case) and found size for radius of bridge as asked.
Assume, 25 1/2" scale, 10" at nut, and 16" at 18.75" from nut this results in about 18.16" radius at bridge. Of course since the bridge for each string is at a different distance from nut this isn't really a true number but gives you an idea, again just for laughs.
Cheers
John