I just finished mine with a Saito .91 and didn't add any weight to get the balance right.

armyrcer, I know exactly how you feel about not wanting to spend the extra $$$ to get a four stroke. The OS61 will pull it fine. The extra money buys sound and feel, but after getting mine up in the air, I've got to say in this case it was worth it. That sound and power go great with the fact that its a bipe.