Our current model looks like this:
Y=4.5675 * X + -.3446
Y= the probability that either a Democrat will win in the district (-1) or that a Republican will win (1).
X=the registration advantage one party has over the other.
According to this model the Democrats have six seats that, logically, if independents voted 50-50, should be Republican due to registration advantages. The Republicans have no seats that have a Democratic advantage.
It also appears that during the 2004 election the Democrats won on average of 60% of the unaffiliated vote.
However, this still needs some work, since this model only explains about 60% of the variation in Y.