A band rehearsal space you say?
Don't know about your area, but that's probably saving you at least $300 a month... well... that's what it's saving your band. This is something we took into consideration when budgeting for room improvements, and I don't at all think it's out of line to request band members to toss in on the action.
While I can appreciate Paul reluctance to start, until you know where you're going; there's also a lot of value to learning as you go, and in terms of porous wall panels, it's really hard to mess it up. (stay away from diffusors and tuned traps... for now) They may end up moving, they may end up being altered, but you won't be wasting $ or time. It's really easy to get distracted with all of the theories here, and forget why we are doing this stuff in the first place. AS soon as we start taking time away from making music to split hairs on marginal gains in effectiveness, we miss the point all together.
In terms of the edge effect, I wouldn't sacrifice having open space between small traps in order to maximize edge effect. There's simply a limited amount of area in corners to begin with, and I'd want to cover all of it. Edge effect, as I see it, is best implemented on the edges of a large trap, where you don't frame in the absorbent, rather, build a frame behind it... so the edges are contributing. Remember, low frequencies travel in waves, not rays. So the thickness of the trap should not only be seen in terms of depth, but in height and width as well. By breaking a vertical corner trap into sections, you are essentially making many thinner traps, as the height dimension IS thickness in a round about way.
[EDIT] Chicago? Probably saving at LEAST $600 a month. Go forth and conquer.