Isn't Jaeggi mode the one that ends with a series of the same letter in the center every session to make sure there's an equal number of matches in each session?

Most of the arguments I could imagine for that being superior are pretty tortured. You should ask Justin for the config file we used. I'm pretty sure we turned Jaeggi on at first but then turned it back off due to that artifact. I certainly found it more stimulating/difficult after Jaeggi was turned back off.