Which rail kit / lighting options for 48 inch tank

[Wind]

Hello,

I currently have the XR30W with single arm stand kit. However, I looking at the multi light rack for our 48 inch length (55 gallon) tank.

Will I need to purchase the light rail on top of the dual arm stand? Are the arm stands same, regardless of whether I single mount or use as rail?

Or can I just buy a single arm stand and use the included attachments to create the light rack?

Thanks.