For anyone who has this in the future, my resolution for this appears to be:
I put the voxel terrain in it’s own map. In BeginPlay of the persistent level I change time dilation to 0.00001, stream the level, then returned time dilation to 1.0. You can’t pause the game and stream a level as it will never complete, hence use of time dilation.
Hope this helps someone else in the future.