Originally Posted by
SansAnhedral
Indeed, the slow speed flight dynamics certainly do indicate that this scaled prototype in the video was 25 kg
That seems like a reasonable number, which should be quite achievable using the foam (either sheet or carved from a solid block) construction used for millions of RC planes. If you wanted to do a mock-up to show to potential investors, as well as having the ability to do demo flights, that would be a good way to start.
Stick a couple of big-ish (110 - 130mm) electric ducted fans in there (up to around 8kg thrust each at 6kW; 5kg would be more common in the cheaper models) and you should be able to fly that around very nicely - at least when there's no wind.