Craig, although using omnis indoors is always risky unless you are in a great sounding venue or are wayyyy up front, you need to make sure the omnis you are using are true omnis. If you are using multi-capsule LD mics on the omni setting you are not getting a true omni pattern, on or off axis; in the case of the healy these are a requirement to achieve the goals off the config.
peace, chris