Persian Style Rice – Water/Oil Question?

OK – This is a question I want answered without people telling me how I should do the entire recipe. I am making the rice in the Persian Traditional Style, including hoping the Tah Dig comes out. I found a recipe, tried it, and did not like the fact that it was not salty enough, but more importantly, it also seemed like I did not use enough oil. The basic process I use is to Par Boil the rice, make a Saffron Mixture (this includes water and oil as a part of it), then put the Saffron Mixture (with some rice) at the bottom of the pot, cone the rice on top, and wait about 10 minutes while cooking it to form the Tah Dig. NOW, after this, you also add the REST of the Saffron Mixture NOT used on the bottom of the pot, and then add some more Water and Oil before turning the temp down, putting a paper towel on top, covering it, and letting it cook.

So, what is the question? The last time I made it, the TEXTURE was PERFECT. I figured out the salt issue, but now I want to ADD MORE OIL. If I ADD more oil to the recipe, do I need to REDUCE THE AMOUNT OF WATER? In other words, do I want the total liquids going in to always be the same, so if I add oil, I should reduce water, or do I always want to keep the amount of WATER the same, no matter HOW much I increase the oil (which will not be more than .25 cups more that I add). Any thoughts on this Water Oil Issue would be greatly appreciated.