Interesting. I did not know that the OPC was officially Zwinglian on the Lord's Supper. This does NOT discribe John Calvin's view, nor that of traditional Presbyterianism.
John Murray described the sacrament of holy Communion as the Holy Spirit removing all distance between us and the Lord Christ. John Calvin insisted the Holy Spirit lifted us up into Christ' presence in Heaven using the bread and wine. This is how certain Calvinists can maintain the doctrine of the "real presence" of Christ, even while calling it the "spiritual presence," not mere barren Zwinglian symbolism & memorial.
I think a Presbyterian who believes Zwingli on this really ought to become a non-denominational evangelical or a Baptist--who are definitely with Zwingli on the Lord's Supper.