AIP4Win MMT does not produce files in the BAA VSS format. It is on my list of things to do to amend the VSS Photometry spreadsheet to read the MMT files, but that is likely to be at least a few months away. (Anyone could create a spreadsheet or other application to do the conversion but I suspect it will wait be me to produce something.)
Another one of the items on my to do list is to investigate building compatibility in to the VSS Database website for loading the AAVSO data format. The main issue here is the last time I reviewed the AAVSO format it did not provide all of the data we store in the BAA VSS database. However, we may just accept that we do not get all of the data.
I’ve not had a chance to look at the MMT format recently, so perhaps you could email me a copy? That will give me an idea of how much work the development will be.
Andy Wilson (BAA VSS Database Secretary)