some cameras have real problems with very short exposures (sub 1ms, near the limits of the bottom of the exposure range), so I deliberately avoid that by using the 1ms minimum. I would try to avoid taking flats with the exposure below about 20ms (at 20ms, the 1ms bias is only 5% of the brightness of the flat, so the difference is 95% of the flat brightness). I don't think I've seen a situation where taking flats with exposure < 20ms would be necessary (at least, not with gain set to minimum).
Using the SharpCap master flat in another application may or may not work well - it depends on what the other application expects... The SharpCap file has the bias level removed in the saved flat frame, but other appications may not expect this, so may want to remove the bias level using a dark flat or bias frame. Other applications will not understand the offset level encoded in the filename, but that's OK because it's not needed if you have dark frames in use anyway. You would need to check the details of exactly how the other application processes the image (sadly I know that in many cases this is not documented) to be sure
cheers,
Robin
