Also check with your PoCo. Their rules may trump the NEC, or your AHJ may choose to defer to the PoCo specs. Either way the PoCo is usually the final word. Also, consider meter base height. That may be the limiting factor here.
Good catch. I was assuming meter/main/combo. There may be state, county, local, or other codes that dictate main breaker height but it won't be the PoCo if the main is separate from the meter.