Even as a "Feeneyite" I could probably stomach Lumen Gentium were it to be taken in isolation. There's ambiguity, implied corollaries, etc. but I cannot detect any direct, postive error that cannot be reconciled with Tradition. We'll get to Unitatis Redintegratio; that's where the "fun" will begin. But, again, even there, I will try to demonstrate that it all flows logically from the very same ecclesiology and soteriology that most Traditional Catholics themselves hold.