You picked a real light engine, I've had a couple of these planes, the first had a laser 80 4 stroke and needed no nose weight, my current one has an os 61 fx on board, coupled with an alloy spinner and the battery poked up as far forward as possible and it doesn't have much extra balancing weight. The 61 is about 6 ounces heavier than the 55, by the time you've added a heavier prop etc it's getting on for a good 8 ounces more than your engine so just add the weight, after you've flown it a few times you can start to remove the additional weight until the plane flies like you want. I found fitting an aluminum engine mount can help balance issues if necessary.