Help with Bortkiewicz/ RH fourths

[muntjack]

Wondering if I might ask a little advice.  I'm currently working on Bortiewicz's Consolation in D flat and I'm having trouble with a section that has a pattern of (mostly) fourths that descends in the RH.  It's a similar pattern to the infamous "Tausig exercise" (think 1-3, 2-4, 3-5) and I am having a very difficult time striking the notes evenly.  one key seems to inevitably sound before the other, which is a problem i don't seem to have with smaller intervals (or octaves). 

  So my question.  Does anyone know of some good exercises other than the potentially harmful Tausig that might help me to strike these intervals at the same time?  I really thought I was beyond this and I almost have the piece complete but I can't have the most beautiful section sounding like falling marbles!