There is nothing wrong at all with a flat finish paint. In fact, it makes the best screen possible when a very wide viewing angle is needed. We use a paint that has just a tad more gloss to it (it used to be called Flat Enamel, but is now called Super Flat) simply because most people don't need literal wall-to-wall image brightness that stays the same and prefer the small boost in on-axis gain.I've seen this mentioned before, but never really could discern why. I've always read that "a slight level of sheen is advantageous" I understand about it adding some gain....but if you didn't want gain....? Does flat blur the image by making things to difuse?