Not sure if this is what you had in mind, ttystikk, but angling the top of the board in- even a slight angle, will direct more usable light to the canopy than will the 90 degrees off the wall, given you have a little extra space and a lighting array that can handle it. You can use a mirror and a laser pointer to drill down the optimum angle.
You're thinking EXACTLY what I'm thinking. In my mind's eye, I'm seeing the light, say a 1000w HID in an adjust-a-wing, endlessly moving around a circle about 3.5-4' in diameter about 18" above the canopy. The plants are arranged in a circular area about 6.5' in diameter centered on the hub of the light rotator, and topped and trained so they are flat across the top and are themselves each perhaps 2.5 - 3' across.
The rigid reflective light panels are mounted around the perimeter of the circle, arranged like a stopsign if seen directly from above. Shaped like trapezoids, top narrower than bottom, these panels are all angled inwards about 25 degrees from the vertical so as to accomplish just what you suggest, reflecting any and all light that would otherwise miss the canopy back down onto it. Better yet, the angle is such that the light would help illuminate the 'dark crescent', that area of the circular grow area that would otherwise be far enough away from the bulb and reflector to receive inadequate light. If the circle of canopy is 6.5' in diameter or less, then light from the adjust-a-wing and light panels would combine to eliminate this traveling dark spot altogether!
What you're left with, then, is a bare (no glass!) 1000w HID bulb that travels in an endless circle only a foot and a half above the canopy, moving fast enough that this proximity does NOT burn any growing tops. Nearly all the light the bulb throws off, even that which is traveling horizontally away from the bulb gets captured by the flat panels at the edge of the canopy and reflected down onto it, ALL WHILE MAINTAINING THE SHORTEST POSSIBLE DISTANCE BETWEEN BULB AND CANOPY. This last is critical, since therin lies the reason why this setup would be anywhere up to twice as efficient as a stationary fixture at getting effective lumens on leaves. The bulb is so close to the canopy at all times that it's like having a traveling spot of daylight, and even the furthest reaches of the canopy would be getting adequate plant available lighting. It would have the maximum penetration due to both brightness and the fact that it's moving to overcome leaf shading.
The panels around the edge of the canopy would need to be right AT the edge of the canopy to minimize the length of travel of any given photon. I want them to be smooth, not 'specularized', since I don't want any diffusion to take place. Diffusion = scattering and it's only employed to help overcome the weaknesses of a stationary light source. Since the light moves, all the bright 'hotspots' travel around as well, eliminating any need for scattering.
For that matter, I am trying to source smooth mirror finish aluminum instead of the specularized stuff for my own version of an adjust-a-wing, again to maximize the reflection and minimize scattering. The cheap batwing reflectors out there use this smooth finish stuff, and it's the best material out there in terms of absolute reflectivity. The shape of the reflector is also very important- the best way to set up the adjust-a-wing for this approach is as wide as possible with the bulb hung as low in the fixture as possible, for the maximum amount of side lighting. Since the angled panels are there to redirect light down onto the canopy, there is no longer a concern that light will be lost just because it's travelling horizontally away from the bulb.
Specularized reflective surfaces, including white walls, all serve to scatter light around- which wastes light by sending a lot of it in useless directions- like into your eyes when you're standing next to your crop, making it SEEM bright when actually what you're squinting at is wasted lumens! With a moving light source there is no need for diffusion strategies of any kind, so instead my approach FOCUSES all available light onto the canopy, relying on the movement of the hood itself to spread the light around evenly.
If you crawl in amongst your girls and look up (with sunglasses on!) from the perspective of the canopy itself, I want you to be able to clearly spot not just one, but at least THREE light filaments; one directly, one in the reflector next to the bulb, and at least one more when you look at the rigid reflective panels around the canopy.
Air movement is accomplished by running oscillating fans up on the walls above the reflective panels aimed downwards, and using the natural airflow coming in from under the edges of the panels near the base of the plants rising up and through the 'stopsign', since heat rises. The shape of the panels aorund the outside actually look and act a lot like a slice of a cooling tower you see at the power plant.
Since you're well versed in how light works, let me know if this makes sense to you, and where my thinking may be awry?
