I HIGHLY recommend the B&S repair kit.
First off for very little money (like $15.00 shipped) you get enough stuff to repair a TON of holes.
Secondly, the stuff works. I mean it WORKS. And it is pretty easy to use. I had holes in the edges of my pleats on my 401 and the B&S kit took care of them quite readily. Application is easy and the stuff is durable. Within 1 week I had a perfect bellows (it takes 1 week to dry).