Ha!
Ed is right.. and so is everyone else. I'll still throw in my 2 cents given the discussion involving all these guys who understand all this stuff from doing it, if only because my interpretation of what we've all come to understand from experience is somewhat different and I think it may be interesting to these other guys, but listen to Ed.
My take-
Microphone pair configurations
can be significant for stack taping, but for different reasons than 'normal' taping situations which deal with more distantly located sources. In stack taping situations the important aspect is the resulting channel differences that create "pseudo stereo" effects, which are different than 'real stereo' effects. Recording PA reinforced sources from a distance isn't a 'normal' recording situation either for a number of different reasons, yet it is pretty much a normal 'taping' situation around here.
These are important questions-
When all is said and done, what really is the benefit of stereo~2mic stealth~stack recording when there is no real separation or sense of spaciousness? Why not a simple, well placed MONO mic. Less to worry about provides greater focus. Count me in the minority. Direct and clear MONO.
In some ways I think you are right Busdriver, and my suggestion to you is to follow that line of reasoning and use one well placed and pointed mono mic. ..then, since you have another mic anyway and your recorder is 2-channel, go ahead and place the other so that you maximize the difference between the two channels while still getting something useful with the second mic. In other words, do something like place it behind you, baffled from the stack by your body, pointing directly away and at the crowd behind you (maximally different while being useful, rather than just maximally different by say, pointing it at the ground).
Then you have your well placed mono channel, and if mixing in some of the different material helps, either in a mono mix by bringing in some added degree of naturalness of the crowd reaction or depth of room sound when playing with the mix level, or alternately by trying pseudo-stereo post production tricks and mixing a two channel output, then great. If it doesn't help, nothing is lost.
There are other reasons to use two mics which have already been mentioned- redundancy, some degree of pseudo-stereo spaciousness based on smaller but not insignificant interchannel differences, maximizing the chance of getting good signal in at least one of the two mics, and getting a degree of stereo width to the crowd and room sound despite an almost totally mono signal from the stack.