Although you have not indicated what recipe you are using, I can tell you that a change from 3.5 cups (no matter how accurately you measure) down to 2 cups is a huge/dramatic/really big change. You could, quite likely, get a wet gloppy mess.
Also, what is the problem you think you are likely to solve?
Think small increments, much smaller. (like 3 1/4 cups, for example).