I've been using this livery for days and i've gotta say how incredible it is. Best APX GP livery for the game. Although I've got a few things to say that maybe can improve the realism on the livery (as you said you want to make the car as realistic as possible):
-The Personal Sticker: In the mod, there are a few options to choose but no options are the in real life personal sticker/sponsor on the inside of the halo which says "IWC Racing" as shown in the pictures below (very difficult to see, perhaps someone has a better picture?)
-Tommy Hilfiger on the halo: On the front wing and side of the car, the Tommy Hilfiger logo is black and white but on the halo (left side) the logo has its original colors (also shown in the picture)
-Numbers on the wing and upper sides of the car: The numbers on the pictures found on google are located in the gold part of the car (above the Mercedes emblem and below the Pirelli logo), in the game, there's a blank space and the number is above all the first sponsors on the wing (above the Tommy Hilfiger logo). On the Upper sides the numbers are correctly placed BUT there's something I've noticed and is that they have an incorrect font and they do not match with their irl counterpart (same with the front wing number).
-APX GP Emblem: It changes the layout of things unfortunately, yeah, some things might appear hidden under the APX GP Expensify logo, but if you don't care about this, thanks to KJxtreme (who he posted the emblem above in the discussion), this should be checked out of the list
-Joshua Pearce as a teammate: Now, I know this one is near impossible to do but if we could change the name and the flag of one of the dark skinned reserve drivers of the game (for example, Jack Tremblay), then we can actually have Joshua Pearce as our teammate (with the use of mods), change his flag from the Canadian to the British one. Sadly, if we make that possible, we would have to find a way to have both helmets, Sonny's and Joshua's, at the same time and assign the helmet to the driver, which I've been testing with mods, and it is difficult.
That's pretty much it, I tried to expand myself as possible so there's no confussions. I'm gonna try and make the first 3 things happen while I also try the last one (which I was already trying to do)