Erin... this somewhat confusing for me in what you are doing here. For clarification ... miniDSP/DL recommends measuring the subwoofer separate from the other speakers. The 2-way or 3-way system with the frequency response outside of the subwoofer range is what they recommend measuring as one speaker (supposedly if they are not too far apart). This is similar to the home... we measure all the full range speakers and the subwoofer separately.As previously mentioned, I tried to use DL to measure and optimize each individual driver to a specific target curve a number of ways. The truth is, it just didn’t work well for me. My best results were met by using DL in stereo mode with the subwoofer getting half of the summed signal as it was summed by combining Left+Right in the routing tab. DL suggests this and my results back this as being the best method. But, again, it might be useful for you to first run DL on each individual driver to let DL tell you the time delay and level values to set for the corresponding output channels in the MiniDSP. Then re-run DL in 2-channel mode after you’ve made those adjustments.
Can you share your XML file.... or post a screenshot of your routing and mixer tabs?
I wouldn't mind trying what you are suggesting to see how it sounds, but it seems like it would confuse the bass management.