You have probably already discovered that but it will save you a lot of time to get some help when equalizing you subwoofers.
When you find a frequency range to adjust, the other person only needs to sit in the sweep spot and tell you when the SPL goes up (or down) when you're modifying the levels/phases or moving the sub(s) around. This way, you don't need to run REW for every configuration. You only do it for the best configuration.
I have used this method a few times and it went really fast. It's a bit tricky at first but works very well when you're used to it
