When using a cluster layer, I find that map panning performance gets progressively worse the closer I zoom in. If I zoom in very close, I can hardly pan at all - the map simply does not respond to my click+drag motion. I am restricting to 20,000 the number of points fed to the clusterer (because of this limitation), but would like to allow millions. Is there any way to improve this behavior? Or is it inherent to the way the clusterer is implemented?