It isn't necessary to remove the trunk to drill the hole for the cables, I drilled a 1" hole for the grommet.
You can also use a 1 1/8" drill, I prefer the 1" hole for a tighter fit on the grommet.

Drilling holes! The CB installation instructions call for metric size drill bits, what should you do?

The CB instructions call for a 7mm, 10mm and a 28mm drill bit, you can use the easier to find inch sizes,
and the antenna installation calls for 10mm and 13mm, listed below are the sizes I used and they work perfectly.
7mm you can use 9/32"
10mm you can use 25/64"
13mm you can use 1/2"
28mm you can use 1" or 1 1/8", I prefer the 1"