I built a Coho from their kit last year. I also drilled the small holes to start with, then used their recommended jigsaw blade held in a pair of vice grips and cut them out by hand. Just take your time and be careful and it'll be fine. Someone else mentioned that it took them about an hour per hatch, and that's about how long it took me too. The hardest part of the job is getting up enough nerve to cut that first hole. :-)

A few other tips I thought I'd pass along:

I also went with the don't-drill-holes-in-the-hull method of mounting the foot braces. Just be very careful when deciding where to place the blocks. I somehow mis-calculated and ended up mounting them about 6" further ahead than they needed to be. The foot pegs are adjustable, so they still work fine, but I had to adjust them back almost to the limit. If someone with shorter legs than me wants to use the boat, they may be out of luck in the footpeg department. Having the footpegs too far ahead also meant that the forward bulkhead had to go a bit further ahead which required some extra trimming to get it to fit.

Here's another mistake I made with mine. When I was laying the hatch lips on the deck in order to trace them to get pattern for the cutout, I misread the instructions. Looking at them after the fact, they seem clear enough but I still managed to get mixed up. They warn you to be careful to leave 3/4" space between the deck chine seam and the edge of the hatch lip you are tracing. Make sure you measure that 3/4" to the INSIDE of the hatch lip. When I was doing it, I mistakenly thought they said the outside of the hatch lip, so the end result is that the hatches are about 1-1/2" or so smaller than they could have been. Not a big deal, but that slightly larger opening would make it a lot easier to fit the 30L dry bag in through the back hatch. As long as I never have to load/unload the boat on that river where they fine you for cussin', I'll be fine. :-)

Good luck finishing your Coho. You're going to love it!