I read the post and was like 'come on man' then I saw the picture and went...there is probably another way to get to where you are going....lol.

Honestly I wouldn't feel comfortable driving in that tunnel because I don't trust other people to stay in their lane. That being said I've found that if you look further out it makes it significantly easier to stay centered in the lane.

If you didn't have an issue with spacing/sides/ect in an open environment do you have a mild case of claustrophobia?

 

After driving tons of cars in varying sizes and shapes, I can say that you should be able to "adapt" to the width of the car. Narrower roads can be a bit scary but honestly the G35 isn't really that different from any other car in terms of its size and shape.

 

I'm from NYC and know all the tunnels including the Holland and I have no issues with it. I have gone quite fast in the Brooklyn Battery Tunnel late night with a wall one one side, and cones on the other boxing me in.

It's really a matter of feeling and knowing your car. When I bought my G took me a few days. Before my G I had a '92 town car which was a boat and I whipped that with no issues.

Best thought I can think of is take your car out on the weekend somewhere quiet like a parking lot with cones and even tap the cones if you need to, to see where your edges are if that's what you seem to need I guess.