i set up at the stage lip in oxford, MS... same type of crowd... ran the TLs XY (cards) right near one of the monitors and it came out pretty well.
with the omnis... if you can get the mics set up between their mics on 2 seperate stands, about 1/3 of the way in, from each side of the stage, with 1/3 of the stage between them, then it would probably sound OK... if you had more cable, I would say to put them up on the far edges of the stage...
i have taped onstage and used DIN, ORTF, XY, and blumlein... never used omnis though.