In the past I have ripped small logs using a fulcrum as a freehand guide.
I think I will try the fulcrum first, since initial cuts are going to be swarf.
I did check the curve on the log, its not too rad. I might try Dave's method if I start making wonky cuts!
I don't know if anybody has seen or uses one of these Adjustable Spline gauges. Its pretty cool for transferring contours to make templates among it's countless other uses. It's just a bunch of plastic interlocking strips that have enough friction to deform to and hold a shape.