The roll cage was first test assembled inside the car. The manufacturer had supplied rudimentary bent plates for welding into the car. Once the position was finalised the areas were marked up for paint removal and hole drilling and the plates were fettled to best fit the shape of the floor pan.
The footplates were tack welded into the car with the rollcage in place. Once tacked the roll cage was disassembled and the plates fully welded in. Then the holes were drilled through the chassis. Infill plates were made to match the contours of the floor where the flat plate could not be welded to the chassis.
Here is the front mounting plate as supplied. This requires shaping, holes marking, holes drilled through plate and chassis, then fully welding in. Then infill plates were made and welded in to fully box the mount to the chassis.