MD1200 shorter rails?

I have 2 MD1200 PowerVault's and a  pair of Rapid Rails for each.  With all my other equipment already installed, the minimum size for these rails won't reach the front and rear vertical square hole posts if that makes sense.  I have 2 choices:

1. Loosen all the existing rack rails and remove the equipment and adjust the rails about a half inch further apart so the Rapid Rails will attach.

2. Get a different set of rails that has a broader range of length.

Any recommendations?  If item 2 what rails would you recommend?  I saw the Rapid Rails II seemed like they had an expansive range but visually couldn't see how the PowerVault attaches.  If it's a shelf it sits on or you attach some kind of slide in and out guides or something.

Thanks.

JR