I covered this in the other thread, but you will probably be shocked to learn there's just a 22.3" difference in overall length from the standard car to the longtail.
Normal F1 - 4367 mm (171.9 in)
Longtail F1 - 4933 mm (194.2 in)
I question that based purely on when Tom P. had his F1 parked next to this one, the Longtail stuck out substantially more than 22".
Well those are the official figures - I'll see if I can find something different later on, or something that can allow a better visual comparison between the two.
Small apology - the source I borrowed that data goofed a bit. The 4,367mm figure for overall length is actually for the 1996 F1 GTR, which is based on the short tailed bodywork, but is still slightly longer than a standard F1 road car.
The actual overall length for the road car is 80mm shorter at 4,287mm or 168.78 in. This changes the difference in overall length slightly to 25.4". Given your earlier comment, I am sure you are still saying "No way..."
Wheelbase of the F1 road car is 2,718mm and the wheelbase of the Longtail GTRs is just 5mm longer at 2,723mm. Doors are nearly interchangeable parts as is all the glass as far as dimensions are concerned.
To give a more visible representation I pulled together these two images, one version with segmented lines to show where certain parts of the cars line up and where the longtail carries its extra length. Click each one to view the high res version.
I think being so low to the ground and significantly wider at the rear gives the impression of more length visually, but it just isn't there.
>8^)
ER