Configure streamCaching in camel.Main

We have an XML configuration with Camel routes that includes this bean to configure spooling to disk for large messages:

<streamCaching id="diskSpoolConfig" bufferSize="16384" spoolEnabled="true" spoolThreshold="10000000"/>

I'd like to configure Camel so streamCaching uses disk-spooling automatically, without having to specify this in the XML config. The Camel instance is started from a JAR with

Main main = new Main();
main.setApplicationContextUri("file:routes.xml");
main.run();

I found doc about application.properties and set

camel.main.streamCachingSpoolEnabled=true

but I'm unclear where this file needs to reside in the JAR so it gets read. I also tried with

    Main main = new Main();
    main.addMainListener(new MainListenerSupport() {
        public void beforeConfigure(BaseMainSupport main) {
            CamelContext context = main.getCamelContext(); 
            context.setStreamCaching(true);
            context.getStreamCachingStrategy().setSpoolEnabled(true);
            context.getStreamCachingStrategy().setSpoolThreshold(10 * 1024 * 1024);
        }
    });
    main.setApplicationContextUri("file:routes.xml");
    main.run();

That was also ineffectual. Maybe it gets applied too late? Because for example when I set context.getShutdownStrategy().setTimeout(5); in beforeConfigure(), it has an effect.

How can I start a Camel instance with disk-spooling enabled?

It is possible to create a context from multiple config files. This allows having presets inside the jar, but loading routes from outside:

    ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
        "classpath:preset.xml",
        "file:routes.xml"
    );

    Main main = new Main();
    main.setApplicationContext(context);
    main.run();