What happens when we expand boundaries across UTM zones?

[mdales]

When we expand the boundary of a project we first convert the project boundary to the nearby UTM zone, as projecting the boundaries out in WSG84 gives the wrong shape being a non-linear projection.

When we project the leakage boundary, 5km, just using the centroid UTM is probably fine even if the project crosses a UTM zone. But at 2000km, does this still lead to a proper undistorted boundary?