You just have to be careful. If you end up having to add too much weight, then it's no good, because wing loading will be too high. I had an easy 2 trainer that I installed the recommended engine on. It was soo nose heavy, that we had to add close to, or maybe a little over a pound of weight to the tail. I think this plane wasn't designed very well at all. Anyway, needless to say this thing landed hot. Luckily It was not my first plane, so I was able to handle it. One day, though, when I was doing some acrobatics with it, I went to pull it out of a dive, and the wings simply folded up. They couldn't take the strain. Be careful about how much weight you have to add. If it's not more than a few ounces, then you should be fine!
The fishing weight idea is awesome. I've never thought of that.