Hey Voltronic, I have been recording marching bands for what seems like forever and thought I would share what I've learned (and btw have learned some great stuff from reading this thread!). I have gone through a lot of mic/recorder combinations, and have been using the AT853 mics for awhile and they are great for the price, and pick up a pretty good spectrum. Sometimes I have to go in through post-processing and cut a bit of bass, but not a big deal.
Think about this...marching bands are designed to be enjoyed primarily from the 50 yard line. That doesn't mean anything else is a bad seat, but someone sitting on the 50 yard line will get the full picture, both audio and visual wise. What does that mean? A pair of stereo mics on the 50 yard line is plenty. There is no real need to add any mics on wider yard lines. DCI (a professional marching band competition circuit for lack of better explanation, which is drum and bugle corps) has screwed up their audio recordings too many times to count. They get screwed up drumline wise (I'm a drumline guy, I pay a lot of attention to this!). When you have a stereo pair on the 50, then add another stereo pair 15 yards out, then you are dealing with sound phase between the microphones. The sound phase REALLY screws up snare and quad sounds, makes them sound like they are playing out of time (or playing dirty!).
So when you watch a marching band, if you want the best listening experience, where do you sit? If you ask 99% of the band people out there, they will say sitting on the 50 yard line in the first couple rows. And I agree. So, your mics should be placed there, or as close to there as possible. Ideally, right in front of the first row is perfect. How high should the mics be? Again, think about what the shows are designed for. The shows are usually designed for the judges in the pressbox, so the horn angles point their sound to the press box. The balance of the brass, woodwinds, drumline and pit are all keyed into making it sound good in the pressbox. So, the mics should be high enough to be almost in the line of sight of the judges as they are looking down from the press box to the field.
I believe cardioid patterns are best, as they are wide enough to get the full ensemble sound, but they reject crowd noise from behind the mics. Hypers can be bad, because they will get whatever instrument they are pointing at the loudest. I have heard XY patterns, I don't think they sound good for this application. 90 degree mic angle with about 19cm spacing sounds good.
Voltronic, I know that sometimes you don't have control over where you set up. If you have to stand on the track, you can still get a decent recording. If you get to go in the stands, front row on the 50 yard line is best. I have a couple samples that I will post when I get a chance. My recording gear all fits in a backpack, I hit record well before it's performance time, and so when the show is ready to go, I pull the mics out of the bag, and just hold them for 10 minutes.
Hope all of this helps!