Child /classes/ possible?

I’m using Events Manager v5.8.1.3 and Events Manager Pro v2.5.1

I know that you can use child templates by creating the following in your theme directory: /plugins/events-manager/templates/template-file.php

I tried creating /plugins/events-manager/classes/em-ticket.php but it wasn’t working.

Is there a way to create a child class file? The default for the “Standard Ticket” in booking is to have 10 spaces, but my client wants to always have 3 spaces. So, rather than edit this every time, they want it to default to 3. I edited the /events-manager/classes/em-ticket.php file directly and that works, but will change back to 10 when they update the plugin.

Thanks in advance,