FYI & Help: Cadillac CTS Spare Won't Work

[tf95ZR1]

I decided to start a new thread instead of hijacking a past thread.
The problem: a spare tire if you run BIG brakes. Up front I have
C6 ZO6 calipers with Fiske 18" rims. Someone smarter than me
realized that if we get a flat tire, the 17" spare won't fit. Fix-a-Flat
won't work if the hole is in the sidewall.

It was said that a 2008-up Cadillac CTS 18 X 4 compact (donut)
spare tire will fit and work. Locating one was difficult since this spare
was only a CTS option. The CTS came with a repair kit including
a mini compressor.

I finally found a CTS spare in Texas. i tried it tonight and not even
close to clearing the front face of the caliper. Diameter is fine. I
would not only need a 1/2" spacer, but have to get longer wheel studs
all around. Anybody have any ideas? TIA!

PS: I asked for Fiske's help years ago and they were of no help.
Maybe now with new ownership I'll try again.