By "38% water discount", do you mean 'water as % of oils", or 'water as % of lye? I ask, because there's a big difference between them, and it helps tremendously to clarify what which one we all mean when talking about water discounts.
For example, Osso uses a 33% "lye solution", which means that they discount their water based on their lye amount, as opposed to their oil amount. If Osso were to use a 33% amount of "water as per oils", the amount of water would be different than if it had been based on their lye amount.
Here is a great PDF that discusses water discounts and their advantages, as well as the difference between basing water amounts on lye or on oil and why it's helpful to specify which method we are using when it comes to talking about water discounts (and also why discounting water based on lye is a more accurate way to calculate water than basing it on oils):
PDF:
http://rivercitysoaps.com/dwcp/dwcp.pdf
Thankfully, SoapCalc gives you 2 different ways to calculate water. I always bypass the 'Water as % of Oil' box and go right to their "Lye Concentration" box to figure in my water discount. Like Osso, I use a 33% lye solution (most times), and I never have any trouble separating soap out for coloring and swirling....as long as I'm not working with a very naughty FO, that is.
IrishLass