Although i'm extremely pleased with the end result I would definitely change a few things to improve the design and function.

SAFTEY - No small children were harmed in making or operating the excavator.   

CATERPILLAR TRACKS - The tracks work very well in a straight line and have a lot of power, however when turning on grass they do struggle.  I would install two drives per track and very slightly curve the idlers to improve turning.  On solid surfaces it works perfectly.

CONSOLE - I would increase the height of console to improve leg room.

SLEW - The slew swings side to side and doesn't lock into place so Im looking to devise a mechanism to prevent the swaying.  If anyone has an idea then let me know.