That's what I did on my SeaSport, and I don't know why it wouldn't work on a Parker. Obviously, you would need to look at what was on the back side so that you'd be happy with the washers and nuts.
For a year or so, I had Roll Control aluminum channels screwed to the fiberglass so that I could remove the gun racks. I'll include photos of that in case you think its something you want to do.
But I noticed that I was never removing the racks, so I figured I'd bolt them to the fiberglass to make them harder to steal.
I had to use a teak spacer so that the guns leaned out far enough so that the tips didn't hit a grab rail on the back of my pilot house.