Re: engine mounts and offsets
You said you have a "Creative Engineering sprocket". What does the sprocket mount to? Typically Jim's sprockets mount to his hub adapter which is a machined aluminum part that clamps around the rear hub onto which the sprocket mounts. They can be positioned side-to-side on the hub to help with chain alignment.
As for your wish to keep the chain within 1/8" of true, that's good, but not absolutely necessary. 1/4 to 3/8" misalignment is okay and shouldn't cause you any trouble. If you are using a chain tensioner it needs to be aligned with the rear sprocket to keep the chain path correct where the chain 'enters' or engages the rear sprocket.
Hope this helps and answers your questions.
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