Re: "Surely this can't be the way?!"

That's the way that I would have done it, though would have had the last frame as zero seconds.

I have done many Flash animations where the first frame and the last frame are the same except the last frame has zero duration.

I think this IS the way. (Otherwise, when the animation completes, then it jumps to the state of the first frame, no morph/tween. Having the last frame same as first, but with zero duration ensures morphing/tweening without changing anything else...)

Peace

James