Hi Nick, and welcome and G'Day!
Cut3D and Cut2d, are mainly designed for toolpathing objects that are designed in another program (CAD). Just out of curiosity, what did you design it in? Looks great, by the way. If you add V-Carve Pro to you arsenal, you can do a lot more. If you go all the way to Aspire, you can do it all.
20 hours seems a long time - what were your feeds/speeds? Also, with foam, you may be able to skip the roughing pass...