Hi Tony,
It will be interesting to see how your results compare with conventional differential photometry. It will give us an idea how accurate absolute flux calibration from a typical amateur observatory actually is. The difficulties compared with conventional differential photometry are you are dependent on stable atmospheric conditions and because suitable reference spectra calibrated in absolute flux are rather widely spaced, differential extinction has to be taken into account – the spectroscopic equivalent of all sky photometry.
Cheers
Robin