It should work just fine... I abandoned TMG quite some time ago to go with the new version of Roots Magic. I find Roots Magic to be just as functional and it has customizable sentences as well. It is the ONLY other software that I have found out there that has witnesses as well as TMG.
The only drawback to TMG is when you export your data it does not translate the witnesses so you almost have to go back and re-do a lot of work. It was worth it to me as while my tree was detailed it was small but if you have a very large tree with a lot of time invested in adding "witnessed" events it will be a major undertaking.
The only thing I can suggest is to write Bruce, the author of Roots Magic, to see if he can do a direct import from a TMG database into RM that will preserve the witnesses.
The more I use some of the more modern softwares out there the more I find that it each one has it's kludges. As I have had to transition from Windows to Mac for my employment I am finding that I am using more and more a web based software called TNG (The Next Generation) it is the ultimate in collaboration software as multiple researchers can work it. It also allows me to share my information in ways I never dreamed of before.
To see it in action you can visit my site http://pagesfromourpast.com
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