Hansons Marathon Method...Anyone?

I have my fifth marathon coming up in May. I have not been happy with my performance in my last two so I decided to try a new training routine. I started using the Hansons Marathon Method. I'm in week 12 right now and I feel great. However, I'm starting to second guess myself a little. Sixteen miles is the longest run they have you do. Am I seriously going to be able to perform well? I'm so used to the prescribed 20 mile long runs that I'm getting a nervous.

Anyone out there done the Hansons method? How did it go in the end?