Nope, regular Sculpey carves and sands nicely after baking. Super Sculpey does not carve so well after baking - it is too firm - but is better for other things. Thank you - when I look at it all I see is how disproportionate it is, and ways to improve it! I think the next one will focus more on detail than symmetry; seems like as long as the bottom is tapered but smooth, it will spin well.
Smoothness actually seems more important than the taper. I found you can spin a plastic Easter egg like a top and it will go for up to a minute, because it is so smooth.