The front of the cage triangulates to the front strut towers. These tubes are coupled to the firewall with a dimple die plate. Tubes also come up from the bottom of the front legs to fully triangulate the front end and protect from tire intrusion into the interior of the cabin.
The driver is pretty far away from any of this but he has many feet of protection from both the unibody and the cage. This is going to be a very safe car!
The suspension is going to be replaced with KW Motorsports 3-Way adjustable, remote reservoir units that are on a plane from Germany as this is being written. Hopefully there will be time to test them and set up the chassis before Super Lap Battle.
The box simply bolts to the floor and is very stiff. For race car builders, the PE Engineering part is the best thing since sliced bread.