First off, are you talking about using Vovin's tek, or Noman's "DMT for the Masses" tek? There is a pretty big gap in complexity of the two procedures. Second, assuming you're talking about Noman's tek, he mentions using 1g lye per gram of bark. When I was first learning, using Noman's tek, I always used 1g lye per gram of bark. Even when using a little bit more water. If you were to use a significantly greater volume of water, then you might need to adjust the amount of lye. As long as you use enough to get your solution to pH 12-13, you should be good.