Who knows how to set up a bass swarm? (DBA)

No, it is if anything even better. Don't know for sure why that is. Probably because smoother. Maybe Duke knows why. All I know is in spite of having 5 subs you never get the impression any of them is doing anything. In the beginning I would even sometimes go over and touch a woofer to make sure it was even connected! 

Read the description on my System page https://systems.audiogon.com/systems/8367 where Mike says " Excellent tonal balance and wide, pinpoint soundstage! Bass was tight and articulate and seemed to be coming from everywhere, but well integrated with the music, band, performance. Never boomy or out of control." In other words the bass is an integral part of the sound stage and imaging. 

My hunch is this is because our sense of imaging location comes from a frequency range quite a bit higher than the subs go. With only one or two subs the low bass isn't smooth enough to fully integrate and so the sense of imaging is weaker. With many subs the bass is very smooth, there's even less auditory cues telling you where it might be, and so the superior imaging cues from the higher frequencies take over and you "know" where it is, even though at that low a frequency there's just no way you would know. 

Ha! Its been a year and I only did this once so I forgot it was level first then crossover! That makes more sense. Level makes more difference and its easier to hear the crossover when the level is right.

Yes they will be better with more subs. The deal is you keep whatever bass comes out of the main speakers and add to it with subs. You do not want to do a crossover to eliminate low bass going to the stereo pair. You want them to get all the low bass they can because the whole idea of DBA is multiple bass sources energize the room more evenly. Therefore if your main pair are full range that's great keep them full range that's two more low bass sources. 

Locating the other subs with a DBA is extremely flexible and forgiving. In fact its recommended they be located asymmetrically. That is, different distances from the mains, the corners, and each other. In my room for example two are along the left wall, two are along the right wall, and a 5th is on the front wall near the left front corner. They are all different distances from their respective corners. 

With your current 2 subs I would try them like that, different distances from the corner. Whichever corner, it hardly matters, and you can try different locations. It seems to me that the more subs the less fussy they are with location. That may be why with 5 it hardly seems to matter where mine are. With just 2 subs right now it might make more difference, you will just have to try and see. 

I would set crossover first, then level. When you get close to the right level be very careful to make very tiny adjustments. If you're not sure if you even changed it that's probably about right. Play a lot of different music at different levels. Take your time. The ear is very sensitive to low bass once it reaches a certain threshold at which point very small changes seem much bigger relatively speaking. Finally when you are really close you can tweak phase, which is really very similar to moving them around. I had a hard time noticing much difference and with me, once I get to that point I figure I'm done. 

What do you mean? African or European?