Am I the OP? I have a V8S with whatever super duper breaks it comes with

I think these are the cliff notes:

19s will fit the car just fine, I run 19" wheels with drag radials.
18s (at least OEM 18s) may/should fit ALL models, including the big brake versions. However, THESE aftermarket Forgestar's do not fit the big brake cars.

 

Doh! Of course you got the V8. Not even the OEM 18s will fit. My 19s had 1/8" clearance with the supers. With the 20s, I have about 5/8"-3/4" clearance

 

Forgeline makes 18" wheels that will fit, with the proper back spacing.
I use them with drag radials on my 2015 Z06, which has the big carbon ceramic disks.
Just make sure that you have enough offset so that the inside face of the wheel clears the brake caliper.

 

Oh yeah? Think these things will fit if I throw on 1" hubcentric adapter or something? I could deal with that for track only purposes...

 

Forgeline will make them hub centric for you. Just tell them the hub center is 63.4 millimeters. They will also make them with (almost) any back spacing you require. The back spacing on stock Jaguar 20" wheels is 7 3/16". Reducing that by 1/2" should give you more than enough room to clear the brake caliper, and will widen the track on each side of the car by 1/2", which will push the tires out closer to the edge of the fender, giving you the "look" many people are seeking.
These wheels are not cheap, but you get what you pay for. They will also finish them in any color you desire. I am in no way affiliated with them, just a happy customer.

 

Since it's an open forum I'll put it out there...not a fan at all. I don't think the style fits the car in the least

 

Hello, I just want to make sure I understand. If I order a set of 18s with 7 and 3/16- 1/2 inch of back spacing the super brakes will clear? Is that similar to offset? Planning on getting some Vertini or Vossen wheels =D.