when you are doing a breakdown that is 200 bps, and the double kick is blasting 16 beats per measure, in my experience it would be more better to the ear if you would just have the bass pop in a little later than the kick, because I found that with the start of the chug, it starts resonating and makes it sort of muddy on me. Could be different for different people. But when I am editing a breakdown at, say, 145 bps doing 16 bpm, I notice that it sounds better when I align the bass with the kick on some occasion, sometimes a little after and a couple times a little before if I want that push to enter in more quickly during the slower rest palm muted breakdowns. It's all about taste, just mess around and you will find the sweet spot. Use those flappy things on the sides of your face! =P you'll get it