Caveat: In the studio I take pictures not in TTL mode, but usually with lighting levels.
Is logical that we should place the flash unit and the reflector "cross" in order to illuminate the long "ends" of the box a little. (With my Metz solution, you can also place two flash units and each bend in the long soft box-ends, that's what it is the luxury solution)
Trust that the flash head of a compact flash unit, the weight of the box "compatible", I would not -
because the (plastic) flash head to hold through / over the 4 screws at points the weight of the box.
Who wants to use a compact flash unit, I recommend a light (rain) Umbrella Soft and appropriate
Holder / shots - or Minisoftbox for at-the-head flash stickable.
I work preferably with old Metz-bar flashes. They are solid and powerful.
Its / their Blitzschiene (s) I screwed on (each) one of the side, above
Retaining bolts with two M 8 nuts. The / the flash unit (s) then I click a fact
as you know it from Metz handheld flash.
(Metz-rod flash units can be converted to fit with a screwdriver to do so)
The lighting control system accepts each an external sensor Mecamat - automatically or with light output levels.
At the lower screw I have a shoe mount attached (the screw through the umbrella holder and screwed to M 8 nut). This on a lamp stand and ready. Oh ... Funkauslöser brauchts yet.
When using two aligned Metz-45 zigern can omit the inner diffuser basically because it does not need its Refexionen.
The light output is exceptionally good - as well as illumination.
I myself am convinced that this dual solution more balanced lighting of the middle bishin to the soft boxing aufweisst than much more expensive soft boxes, which are fired with a single studio lamp centered and internal diffuser.
(These are in my opinion, correspond to the light output, roughly the use of a single rod lightning in this box.)
IMPORTANT: do you want to Metz-45-ties, which want to use it directly to a digital camera, you have to take 3.4 or 5 models.
(The CT1 he have too high trigger voltage and can. Zerschießen Cactus Funkauslöser tolerate this tension the Camera).
I wish you good light ... and hope my lines help one or the other ... :-)