I used to eat a meal, sometimes a big one, and dose right afterwards. Most of the time it kicked in faster, with less nausea, and was more intense. Though the downfall was that if I puked, it tended to be very thick and nasty. (This was also with CCC, I strongly discourage anyone from using this and I no longer do myself.)
Off topic a little, but the first time I had any dxm in a while I'm coming up strong and my brother in law comes in and wants me to help him get a fly out of his ear. Wrong time to ask such a bizarre question I tell you what.