Use custom SpotBugs plugin in multi-module maven project

Question

I have create a custom SpotBugs plugin for maven like described here in a multi-module maven project. But I cannot figure out how to use it. There really is not much documentation or examples for this.

Like described here I have used pluginList and plugins configuration properties for SpotBugs. But it does not report the bug when I run spotbugs:spotbugs. Other bugs are reported. Any idea what the problem might be?

I am using Spotbugs in maven like this:

    <reporting>
        <plugins>
            <plugin>
                <groupId>com.github.spotbugs</groupId>
                <artifactId>spotbugs-maven-plugin</artifactId>
                <version>${spotbugs.plugin.version}</version>
                <configuration>
                    <pluginList>custom-spotbugs.jar</pluginList>
                    <plugins>
                        <plugin>
                            <groupId>com.example</groupId>
                            <artifactId>custom-spotbugs</artifactId>
                            <version>${custom.build.version}</version>
                        </plugin>
                    </plugins>
                </configuration>
            </plugin>
        </plugins>
    </reporting>

Edit: I noticed that I had to run mvn site for the reporting plugins to work. But the next problem is that the configuration values cannot be changed. I had <effort>Max</effort> in the configuration and even if I remove it, it is still used. Are the configuration cached or something?