I have been toying with a number of options to help optimize the map marker display.
Does the current marker system support viewport marker management? Your team has employed clustering, but there is a method to limit the markers to the viewport as illlustrated here: https://developers.google.com/maps/articles/toomanymarkers
Is it in there or what would it take to get it implemented?
Please let me know. This would be extremely helpful to my cause.