BurtC,
I sold the camper, so I have no measurements to give you.
I centered the table mount on the side wall. I believe the table bracket was offset a bit from center of the table top, but I'm not certain.
Of course, there are dimensional differences between the TC650 and TC800 that may affect your installation.
I'd recommend clamping the table top to the bracket and try different locations.
The picture of the Lagun table on the TC800 page of Northstar Campers website looks centered to me. I'd start there. You can also call Northstar directly and someone can probably talk you through the installation.
Good lock with your Lagun table. It's a real step up from the original table system.