I visited the battlefield about a week before this year's anniversary and listened to a park ranger giving his opinion that the loss of Little Roundtop might not, probably would not, have made a difference. He pointed down the line (Cemetery Ridge) and basically said, "you MIGHT be able to bring 2 guns to fire down the line, but that is about it. The cleared area is just too small when firing to the north." It also assumes that the Confederates could have gotten guns up there during the melee, or captured Union guns intact.
A bit revionist. But I had to admit that he had a point about the gun line being too narrow.
Plus, it's questionable to say that Chamberlain's death alone would have meant the collapse of the Union effort on the Round Tops. He was a brave and inspiring man, no doubt. But I suspect the Union troops on those hills were all too keenly aware of the outcome if they broke.