You should investigate 'Member Groups'. Alternativly you may need to generate custom levels eg. if you have 80,000 customers you may want to create an A-Z level.
Somethings to remember, if you do have 64,000 members under a parent and a user drills down, what will be the result - a large hit on the server (good aggregation will help), the client side software may bleed and die horribly and if it didn't who on Earth would enjoy analysing the data with so much scrolling to do.