The 2nd photo shows the mounting plate with its "mounting plate seal" in position ready to be matched up with the mounting bracket.
It seemed obvious in hindsight but there is no need to drill a 22mm hole in floor of the vehicle to insert the mounting plate through if you have an assistant to get under the vehicle and place it in position from below.
So why did I still drill the 22m hole on one side before realising what I'd done? NFI. Brain fade brought on by too many hours crouched down in the back of the Disco with my sciatica giving me hell - that's my excuse. In the end I had to get under the car to do the other side as my wife's arms weren't long enough to reach up to the floor...
I squeezed a good amount of their "Tekote Sealer/Rust Preventative" around the union between the vehicle and the mounting plate. Mattyg also mentions applying an additional sealant to this area - a good suggestion...must remember to get under there again soon and do that.
Final note on these floor mounts - have a look at the final pic to note the fuel lines that will be directly below where your drill bit is exiting the floor of the vehicle. Best not to go to deep with your drill in this area :angel:
You can also see the 22mm hole that could've been an M10 hole.

