Flee Market

A number of years ago, I let a mistake go which I have been wondering about. In ט"ז:ל"ד, the word נָסוּ should be pronounced NA-su with the accent מלעיל. However, it was mispronounced na-SU, מלרע. My compunctions are based on the possibility that moving the accent to the end would make the word derive from the root נסיון. However, I can't recall ever seeing such a word in form. It would be נִסוּ (with a חיריק.)

Thoughts?