Override spring-boot EurekaInstanceConfigBean

I am building a dockerized spring-cloud based microservice that registers with eureka. Part of the registration process is asking the host for the port mapped to the container so docker can choose a free host port for the containerized service.

I have a host based service the dockerized service can ask for the port mapping and am now trying to register the microservide with eureka using the external port.

I get the right port inside my microservice but am unable to override the EurekaInstanceConfig.

What i have tried:

@SpringBootApplication
@EnableEurekaClient
public class ApplicationBootstrapper {

    @Value("${containerIp}")
    private String containerIp;

    @Bean
    public EurekaInstanceConfigBean eurekaInstanceConfigBean() {
        EurekaInstanceConfigBean config = new EurekaInstanceConfigBean();
        String hostPort = new RestTemplate().getForObject(
            "http://{hostname}:7691/container/{id}/hostPort", 
            String.class, 
            containerIp, 
            config.getHostname());

        config.setPreferIpAddress(true);
        config.setIpAddress(containerIp);
        config.setNonSecurePort(Integer.valueOf(hostPort));

        return config;
}

My custom EurekaInstanceConfigBean gets created but the configuration is not picked up (the service registers with its internal container port).

The question is: How do i override the EurekaInstanceConfigBean?