This is a picture from when the radio was first installed.
The black plastic piece that the dome light is mounted onto and covers the wiring is removed
so the VHF wires can be run from the radio into the roof.
You can just see part of the roof access hole in the upper left
edge of the picture. I run my wires through that hole and then
go through the roof inside my tuna tower frame tubing to the antenna,
or down the back edge of the inside of the cabin to join with the rest of
my wiring harness.
If your roof is double lined, using self tapping screws through the
carpet and though the inside liner backing should be no problem since you
won't be accidentally punching any holes though outside exposed fiberglass.
I don't know if all years are double lined like that though.
I think they started doing the plastic wiring covers along the back cabin edge in 2007.
If you have an older model Parker that doesn't have the wiring drop and cover
down the back edge of the cabin, I'd just run it straight down from the radio
to the dash along the window frame corner like Sully and Capt Ron's install.
Plastic wiring cover along back edge of cabin:
Wiring cover removed showing wires from VHF, spreader lights, anchor light, horn, and
whatever else is on the roof dropped down to join the rest of the wiring harness:
