LOL, if it were only a stomachache you had to worry about...
no my friend, it is much worse than that. If you have a poorly timed SWF, you may end up with an extremely embarassing "accident" if you get my drift.
You really need to allow two hours. Some people do the SWF (Salt-Water-Flush) and then leave, getting to work to do the bathroom duty. I myself would never dare to try that because my SWF's have been somewhat unpredictable -sometimes kicking in a little at half an hour, other times taking their good sweet time and taking two hours.