Edit 2: judging on the lack of replies I start wondering if my issue is clear enough. Please tell me if I need to elaborate more.
Notice: see bottom for a co
Try stretching the window of the player, both bigger and smaller. If that has a significant effect on frame rate, your fastest and easiest way to improve performance is to shrink the size of the stage. This tends to be an unpopular answer when presented to people - especially artists - but if your bottleneck is in the size of your stage, there is not much you can do in code to fix that.