Why are you using the word, radius?
Radius 'often' implies a sphere.
In this case: an enormous sphere.
And with the case of any sphere, even with the universe, there's a center.
Interesting point, since the BBT implies a spherical expansion of this universe, the center appears astonishingly....anthropic....according to humanity's point of view....Leaves you wondering if maybe Ptolemy had it right all along.
Today's cosmologists would violently disagree with my viewpoint.
SBI.
Jacob