Downunder: I've also been trying to figure out a way to determine the coefficients experimentally. I think that the method you are suggesting would be complicated by the fact that the dimensions of the tube itself (length, diameter, etc.) would change with temperature, and the methanol and nitro would start to evaporate as soon as they were put in an open tube.

By the way, I put together a Microsoft Excel spreadsheet that does fuel calculations such as % by weight to % by volume, how much oil, nitro, etc. to add to up the percentage, combining two fuels, etc. I have a versions for Windows ME, and one for older windows versions. If anyone wants a copy, E-mail me direct.