I'm pretty sure they do a rack specific version of that - with flange either side of the lamp to put your bolt through - or have you already made your purchase?
Like this? Or have I misunderstood you completely? - Which I think I may've ;-), and, on reflection, I see little reason why what you've written there^ wouldn't work.
Were it me, and with a nice light like that, I'd consider putting a lock-nut on the bolt on the inside of the rack mount, if you have the space for it.
Or even a half nut if space is tight.
I'm pretty sure they do a rack specific version of that - with flange either side of the lamp to put your bolt through - or have you already made your purchase?
Like this? Or have I misunderstood you completely? - Which I think I may've ;-), and, on reflection, I see little reason why what you've written there^ wouldn't work.