I am wondering if there will be a way to allow larger files (over20mb)?

HI Barry,   Good question, but unfortunately we can't really give you a specific answer.  In the grand scheme of things, faxing over a VoIP network is relatively new.  There are still an awful log of analog fax machines out there.  There is a pretty complex process for the conversion and transfer of data as it travels from one fax system to another.  Larger file sizes tend to have higher failure rates.  As the technology continues to develop I do think that it is highly likely that larger file sizes will be supported, but it's really hard to give any sort of ETA. 

Mike