wouldnt it be ok to use a far red light? You said this is about 720nm, well thats nearly infra-red. If you illuminated the plants in this light throughout the "night" then the Pfr that's converted back to Pr by the process of creating florigen could be continuously converted back to Pfr by the far red light, possibly speeding up flowering. Does this make sense? I'm not an expert, but this makes sense to me from what has been said here (unless I got the wrong idea).