I'm installing a new 125A distribution panel as a branch circuit off the main panel in a residence. I bought a 200A Siemens panel at the big box that had the ground bar and was supposedly configured for this, but the main breaker they carry for this panel (4x breakers wide, oriented so you push down on the yoke to turn off.) doesn't fit! Which is to say, it fits the panel, the bolts line up, plenty of clearance, etc, but the punchout on the cover is in the wrong spot. Searching for it online, the part# only seems to return more of the same. Siemens website lists the part for $477, but even though I've already got several circuits run, I'd replace the panel before I wasted that kind of money.
Is it acceptable by NEC to just take a grinder to the cover and put a cutout where it needs to be? What's the proper way of closing up the "wrong" cutout? It will end up being an L shaped hole on one corner of the new cutout. Thanks!
