This stuff works great!

http://www.marineformula.com/index.htm

I ordered it online.

I also used hard wood wedges, a long bladed razor knife, and some plastic scrapers.

Did both of my Dana Tabs at the same time, and it took about 2.5 hours.
I would slice some, spray some marine formula on, wait about 10 minutes, then drive the wedges in a little further.... repeat. I had some guitar string waiting in the wings if needed, but didn't end up using it.

No damage to the gelcoat.

Chris