[DanDan]

Well well. Clearly 'scattering' elements above an SC cloud would prevent flutter and provide maximum return of diffuse sound from the overhead coupled space.
In the linked pdf Jeff Syzmanski uses absorption in the over space 'to prevent flutter'. I assume the use of absorption up there will indeed prevent flutter. However it would also bring down the overall room decay time and somewhat diminish the return of diffuse sound downward. This might be exactly what is required.
These are two different approaches, with slightly different goals. I don't think either could rightly be called 'wrong'.

The room has splayed walls, it may or may not need much or any additional absorption. So if one was to go with Space Couplers, which I would love to see done, the choice of scattering or absorptive devices over the couplers would be dependent on the desired room decay time. Many instruments won't record well in a washy room.
Given the 15 foot ceiling, and the cost requirement, the simple and cheap hanging bent panels could perhaps be the scattering elements.
IMHO, the best possible design here would be a checkerboard of scatter panels and absorptive panels. Perhaps with different concentrations of either at opposite ends of the room to give a variable acoustic to suit different instruments, vocals, etc. Space Couplers could be installed underneath, again not necessarily over the whole ceiling. Some recorded sounds do not benefit at all from the return of early reflections, even after 20mS. e.g. Vocals and perhaps drums, due to the high overhead mics and moving cymbals. Also I have not seen much testing of Space Couplers. In the pdf we see a picture of them over a drum kit. It has been suggested to me, by a practitioner who actually uses these, that they are superb under an absorptive cloud in the mix room. I have not seen tests or testimonials as to their use over drums however.

DD