(Part I)
I don't think the horizontal needs to be at parity.  The horizontal member of a cross is shorter than the vertical.  
If a priest says mass by himself, is he less in communion with the rest of the Church?  Of course not.  First and foremost, the Mass is a sacrifice and practice of the virtue of Religion.  It is not self-reflective, though it may give rise to that, nor is it, strictly speaking, oriented toward any other that God.  However, even though the mass is oriented to God, it does not negate the fact that when we hear mass, we also do so in greater communion, both with those present and those who are members of the Body elsewhere.  The Minor Elevation is the high point of the mass, and it is certainly not (or shouldn't be) a witness to our own Redemption nor should it be a consideration of anyone other than God.