Your AKG 62 caps are definitely what you want to use if adding omni. But most people here add more mics to highlight an instrument or add dimensionality, not to correct a setup that doesn't sound good to begin with. I would use some post-processing to see if you can get the sound you're looking for. The Neumann's are great mics and capable of outstanding recordings. You also might try a different mic configuration. ORTF is not usually the go-to method for the situation you describe. You could try ORTF or NOS on stage, or DIN further back, or spaced omni, and get a feel for that room. I think those options could create better recordings as first options rather than adding more mics.