Restricting Record access at a center / site level

Hi all.

We have a request to setup security for a custom entity to only allow users to view records created for their center. Normally i know i could just create individual BU's and just give access at the BU level in security roles.

The problem here is that there are many centers. Do i want to create 70 or 80 BU's or would there be a better way to manage this?

Thanks