My thanks to Andy and Robin for their helpful advice. I was aware what is held in the DB but that explanation should be useful to others. The suggestion to contact the PI is a good one and as I will be keeping all the raw (but calibrated with darks and flats) images that will remain a possibility for those who may wish to re-analyse my data.
Most people, though, are unlikely to be that finicky and would like to have an overview of the light curve which is sufficiently good for their purposes without having to spend a great deal of effort. With that in mind, I will stack the images such that the integrated SNR is at least 30, yielding a statistical uncertainty of ~30mmag, easily good enough to pick up the pm 110mmag variation reported so far. As the database holds an explen field for each entry, I don´t see that it matters whether three subs or a dozen are stacked for each individual measurement — as long as the total duration and effective mid-exposure time is recorded of course, as it will be.
FWIW, I store essentially every image ever taken, with its metadata in a PostgreSQL database, because disk space is cheap and I have yet to reach even a terabyte of data. Multiply that by a few hundred observers, especially if they are taking high frame rate videos, and I can see it starting to become a problem.