I can't think of how you would keep the buy-in and pay-outs etc straight not to mention the bust-out stuff trying to run two tourny's at the same time with-in one loaded copy of TD. An idea i had, and just tested, failed. I thought maybe loading two copy's of TD, and just alt-tab from one to the other as you changed games. But TD will only load once. I even tried to copy TD into a second folder on a diff drive and get it to load again from there, but it won't. It sees that it is already loaded and just switches you to that program when you try to load a second.
Another idea that should work fine is this. Load and start tourny one. After round one, pause and save it. Then load and start Tourny two. After round one is over, pause and save it. Then load Tourny one again and it will start from where you left off. In fact, if you have it set to auto pause at the end of each round then you don't need to pause it. Just save it and load the next tourny. Just be sure you give both Tourny's a diff name so your not over writing one.