All covers must be accessible,a removable panel would possibly be ok,but it sounds like you are trying to do this the hard way.Rigid steel conduit would only be necessary if the panel is more than ten feet from the meter,all the other methods posted here would be acceptable,however your local rules may vary.
This is the kind of stuff that drives me bonkers on projects like this. Endless trips to Home Depot, Internet being out for a week killing my research and limited time off work. After my experience with the building contractor, sub that put up the building and loser engineers that drew up the prints, I just don't want to spend anymore money paying people to do the job that don't really care about their work, that is why I am on here.
I originally hired this out to an electrician who I was going to pay good money to do the work. When the old fart from the electrical company came out to pull the fuse at the transformer, he basically scolded the electrician and pointed out that the electricians plan was a joke and refused to turn off the power in order for him to even start work. So that led me to this.
So let me start back at square 1. If I want to conceal the wiring from a flush-mount 320 amp meter base over to a 200 amp main breaker panel, how do I do it? Is it even possible?
In order to make 2" 90 degree sweeps fit, you have to make an oblong hole in the wall because the bend falls right on the stud.
I used this method make a run in the opposite direction to a 200 AMP switch that goes to the house. I used the center hole in the bottom of the meter panel for that, so it's already taken. Using the center hole allowed the straight part of the 90 to fall right at the stud so no hole enlargement was necessary.
Now, I would like to do the same thing but since the center hole is already taken, I am limited on options.
Perhaps I should take a picture?
The other solution that I came up with that would work is use a side exit hole in the meter panel, put a 90 there pointing up, hook it two 45's which would move it back the opposite direction, then a 90, go through the adjacent stud, and another 90 into the top of the breaker box.
All my solutions just seem so unprofessional and with the building bust, there just aren't any installations I can reference. In retrospect, it would have been a lot easier had I had I not chosen to flush-mount the meter box.
Including checking L&I for licensing, bonding and any outstanding judgements etc. 