"For the LE 85 it seems that the red terminal is positive."
I wouldn't be too sure about that.
Oh the fun and joys of working with the 2420/2405 combination. As is, you will never get rid of the dips no matter how you wire them. There will always be an interaction between the two units. But contrary to your statement, when wired differently, the dips are not the same and it comes down to picking the lesser of two/many evils! (Been there done that, give me a Heil.)
If your tweeters were mounted externally, you could also create/fix dips by moving them forward/backward until you eventually find the smoothest combination in your room.