Ok, here's how I ended up doing it.
google.maps.event.addListener(map, 'mousemove', function(event) {
///
var overlay = new google.maps.OverlayView();
overlay.draw = function() {};
overlay.setMap(map);
///
var point = map.getCenter();
var projection = overlay.getProjection();
var pixelpoint = projection.fromLatLngToDivPixel(point);
///
var thelatlng = event.latLng;
var proj = overlay.getProjection();
var thepix = proj.fromLatLngToDivPixel(thelatlng);
var mapBounds = map.getBounds();
var mB_NE = mapBounds.getNorthEast();
var mB_SW = mapBounds.getSouthWest();
var nE = proj.fromLatLngToDivPixel(mB_NE);
var sW = proj.fromLatLngToDivPixel(mB_SW);
var north = nE.y;
var east = nE.x;
var south = sW.y;
var west = sW.x;
var appx_north, appx_east, appx_south, appx_west = false;
if (Math.round(thepix.y) <= Math.round(north+20)) {appx_north = true;}
if (Math.round(thepix.x) >= Math.round(east-20)) {appx_east = true;}
if (Math.round(thepix.y) >= Math.round(south-20)) {appx_south = true;}
if (Math.round(thepix.x) <= Math.round(west+20)) {appx_west = true;}
if (appx_north) {
pixelpoint.y -= 5;
point = projection.fromDivPixelToLatLng(pixelpoint);
map.setCenter(point);
}
if (appx_east) {
pixelpoint.x += 5;
point = projection.fromDivPixelToLatLng(pixelpoint);
map.setCenter(point);
}
if (appx_south) {
pixelpoint.y += 5;
point = projection.fromDivPixelToLatLng(pixelpoint);
map.setCenter(point);
}
if (appx_west) {
pixelpoint.x -= 5;
point = projection.fromDivPixelToLatLng(pixelpoint);
map.setCenter(point);
}
});
There may be a more efficient way to do this, but nobody has said anything, and this works, so it will do.