Thanks for the suggestions, I’ve made the precomps and added timewarp, but as feared the animation is now slower, but blocky and unsmooth.
It’s slowing down the time between the frames but is not adjusting the stroke effect’s distance between frames. For instance if I had a 10 frame animation reveling the image, Timewarped it’s now 20 frames long, but they are the same 10 frames over the course of 20, each frame is just doubled.