I think Luther agreed with Paul and Augustine and the early Reformers regarding the truth of double Predestination. Single Predestination is really no different than what the RC and Orthodox posters are saying.
Here's a link to an excellent article:
Humanism has attempted to work its magic on men and God's will since the garden, day by day trying to chip away at God's sovereign decrees. Single predestination seems to be just more hedging of our bets, giving men the credit that belongs to God alone.
I agree with Dr. Eckleburg. If salvation by faith alone is understood, following Luther, to exclude human cooperation with works of free will, then single predestination makes no sense, it is double or nothing.