Thanks for the tip. I unfolded the screen again and this time I placed a 1/4" diameter rod in each crease and folded the screen around the rod. After I did this the screen fit snugly so I don't think it will move. It has the most resistance when moving toward the opening to the breather tube. It moves a bit easier toward the drain hole but it seems to be snug enough so it won't move. I will check it again tomorrow to be sure it does not relax enough so it moves easily again.
