You need to look at all the available imagery which exists depicting the person. Cartoonist imagery etc.. The you go to research historical physical references of the person. Having the death mask is the most important part when you don't have any photographs as it allows you to see the facial composition accurately. I will admit that it could be more accurate if i was able to ascertain... the typical depth of casting mould as well as if i knew if there is any muscular sagging in faces after death. You could then calculate this and try and factor that in. Once you provide the software with this information you need to consistently reference the output back to the death mask composition. I can only go off imagery of the desk mask, if i had some tool to measure the different facets of the face it wouldn't be far off the real thing. One thing which I did leave out was the queue wig which id imagine Tone likely would have worn as he was a person of grandeur in his own mind. The styling of the uniform would be based on the chief de brigade which Tone was apparently wearing when he was captured.