Loading scene with ImageTarget disabled

Hi there.

For my current project it would be very convenient for me to start my scenes with the Vuforia image target objects (those with the ImageTargetBeahviour and TrackableEventHandler) disabled and then enabled them when required. However I've found that if they are disabled when the scene is loaded the tracking doesn't work. I also noticed that if I load the scene with them enabled then I can disable/enable them and they will keep working with no problem so I guess some kind of 'image target registering' which find them only if they are enabled is happening when the scene loads. Am I right? more important, is there any way to have them disabled at the load and then enable them?

Cheers!