Static mesh model size of Earth Collision map won't work

So I’m trying to recreate a sphere that’s 726900000 cm in diameter and then create a person that can walk on it. the problem is I can create the sphere that big but when I try to place a Playerstart on the surface, it either doesn’t work or I’m spawned way above where I actually placed the spawn and my character falls through the sphere.

How can I create a collision map that will work with a sphere that big? or what am I doing wrong with the Playerstart?