I'm not sure we have a problem here.
If real world lateral Gs without specific setup is 0.93 and game lateral Gs is 1.00 with tinkering I'd say that is a pretty damn good hit.
As I said earlier, I disagree that this car should have any downforce (more than lift) at all.
There's some unclear things about the car, like if they lock out Weissach or not. If they don't, for sure that will influence the coast + cornering stability by providing potentially more toe-in than my system currently does. We can't really do it correctly, but I still have some tricks up my sleeve.
I can get my C2 to pull exactly whatever G is specified IRL, be it 0.83g or 0.86g, by tweaking tire grip up or down slightly or wearing the tires more or less. When it's so close it comes down to things like that. I think right now, it pulls about 0.82 - 0.83g holding a 60km/h turn. Mind you that a 1990's RS on 1990's tires pulls 0.90 - 0.91g.
With that in mind I find the 0.93g very hard to believe with modern tires. Put semis onto a stock C2 and it'll pull more than that, and the balance and LLD is way worse. We don't know enough; they could have pulled the skidpad G after overheating and wearing the tires down after all the other testing. It could be an old set to begin with. We just don't know enough. If I had more reliable info, I could make better guesses on the tires; but everything I could find about the set describes it as a very grippy set, and I've put mine on the low end here, not high end. The ballpark has more room up than down.
Look, you'll go into "more downforce than lift" territory by just lowering the car 50mm. Eliminating some of the flow from going under the car and funneling it over will probably net you a little bit of downforce total from the front aero elements; and this is with the stock aero implements, although they are quite good. I don't have data specifically on a 911 with front spook, but the rear spoiler is more aggressive for one, and I've never seen wind tunnel/CFD readings with a spook where lift didn't turn into downforce. Although those were always somewhat larger implements.
If you have some actual basis to back up your idea, like empiric data which supports it, please post it so you can help me. If you have some 911 wind tunnel readings with spooks, I'd REALLY want to see them. Thanks.