For Lighting, maybe Start with something, like i did Here for the 20kfps Shot:
forum.krontech.ca/index.php?topic=521.msg4950#msg4950
I Put one of my 300 Watt Lights Right Behind the Subject, because i needed to Close the Lens down very much, to get a Lot of Depth of Field, while also running 20kfps. This of course will make the Subject look very Dark --- Keep in mind this is an Actively Burning Sparkler / Fireworks, so in it self rather Bright Object. But it will ensure you that you will get somewhat decent Image Quality overall and you will be able to See Silhouettes, if that fits your Task; but Details in Texture or of the Surface itself Might get lost.
That should at least make it Possible to Record a bright enough image with that one Light you got.
From There you can Try to move the Light to ABOVE the Sample, shining Down on an angle from the Direction of the Air Gun, as close to the Sample as Possible without being in the Way or in Frame.
Thats Where i would probably have that Light in this Situation...?
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Regards Framing, you can still try to start with some Less Extreme Settings like 5400fps, which will give you a much more Square Aspect Ratio. If the Lights are Set up right, you will still get a lot of Information from that Recording cause its much cleaner and better Visible, and can then decide which Part of the Frame you want to Record at the Very High Framerates if needed.