Question about backfeeding grid

Jeffco

I currently have 400A service to my house.  Comes into a Milbank 320 meter panel that also contains 2 200A individual breakers.  One of those feeds goes to my 200A house panel, the other goes to my 200A panel in my shop.  I'm planning an ~16kwh solar system with ~30kwh of battery backup and I want to tie to grid.  I'm currently planning to use the EG4 Flexboss21 inverter and one, or two if needed, Gridboss units (if 2, one in house and one is what I envision).  I want the solar and battery backup to be able to power it all if the grid is down.  The batteries and flexboss would be in the house garage.

I'm struggling to understand how/where would I tie the solar power in to the grid with the main service/meter panel setup.  Would a line-side tap be the answer, if my util company allows?