Hello Mark,
I'm sad to tell you that your helmet will not pass basic approval for 501st. You seem to have the first generation of AM armors with the old helmet that resembles the FX, but, with a smaller dome. Here is what the CRL says about this type of helmet:
Note: The helmet is accurate in detail and proportion to official references.Many commercially available helmets or those considered disproportionate in size or shape are ineligible.