the scale had me at 140lbs and I am only 120. I have a feeling the scale is probably a lot better at reading on much heavier weights. Like I said even if the car is 100lbs heavier that the display I am still pumped at the results.
I will have to do some exploring on the chassis to see what can be done about bolting large plates. There are some spots there the alum is very thick but it will just take some figuring out. I found a tech article that went through the generations of manufacturing and design on the A8 that was fascinating. I need to find that again because it had a ton of pics through the manufacturing process that might help me out. I think something like 40% of the car is glued together and the rest is laser welded .
What you could do is create additional cage members that would spread any crash loads across a greater surface area beyond that of a traditional 6 - 8 point cage. For example a horizontal on the main hoop that was close to the floor would rest on the drive shaft tunnel. Door sill bars than ran from the A-pillar bar to the main hoop would “catch” the floor in the unlikely event that a mounting plate failed. You could even build a cradle along the floor from sill bar to sill bar to mount the seats too. That way seats are cage mounted and not car mounted. In my head I am thinking of ~24 ft of extra tube at 1.5~1.7# per foot, all below the CG height.