Oh Spirithorse I've worked with the spiral blades, they have a purpose in Scroll sawing but I don't like them for cutting as they simply consume to much wood when one does real small frett work. I like them when you want to high-lite a line as to make it more visible and to clear away large amounts of wood.
I have also used them for backwards cutting as you suggest but again I find them to consume to much wood, maybe I'm doing something wrong.
Thanks for your suggestion, This was not for a project I'm working on right now but I'm thinking of doing oriental Privacy screens they are 60" x 30"
.../Hans