I used an angle grinder with a cutoff wheel to cut it about 1/2" from the hull because I was also worried about slipping and cutting into the hull. Then I used a multitool like this to cut it almost flush to the hull so I could finish smooth it with a 80 grit flapdisc on the angle grinder.
The multitool blades that come with it (shown in pic) get destroyed by fiberglass; I ended up getting the the abrasive bit for tile and that worked much better.