Hmm.. by watching the flame?
I start out by knowing what the flame ring looks like under a pot with out a windscreen and I also know how long 1/2 ounce of fuel will burn untill the stove goes out. I then placed a windscreen with out holes in it to see what happens to the fire ring. The windscreen being in very close proximity to the pot(1/4" all the way around) If the flame reduces in size, then we know we need to add holes. So we add holes and do a test all the way through using 1/2 ounce of fuel. We do this untill we have acheived the best results with the fewest holes.
A windscreen with holes only on one side will cause an unwanted draft the will blow the flame to one side of the pot and the flame will go up the side and be ineficient.
Try doing a video of the inside of your house just to see how your camera works in the video mode. See if there are adjustments you can make before you do an outside session.