Server Side Track API Limited to 2083 char payload on URI (get)

According to documentation, when registering a server side track event, I am to use GET and include the payload in the url. The payload is a json document that is base64 encoded. No problem.

However, when sending an order placed event including addresses and items, it is very easy to exceed the 2083 url character limit, which throws an exception, and makes the method call unusable.

Can I use Post instead, and include the payload that way, and if so, is it still base 64 encoded, or just the json payload?

Thanks