There IS no science on down fill power, just regulatory standards which were relaxed under the Bush administration. Therefore, 900 cubic inch down is 2005's 800 cubin inch down.
This is largely true. Here and there you can find some published papers on some more basic science aspects, but these are generally isolated and not a part of any unified effort.
One professor at UC Davis has published several papers with a series of graduate students. I have lost the link to his website and list of citations.
There is little visible benefit to the equipment making industry (sleeping bags, and garments) to invest in down science.
There are a number of people who are "experts" of the consultant sort who may write on some outdoor discussion boards. I have found that their writings often cause my brain to slowly fry. Not just because the writing style is blurred, but because the statements made often make no sense.
I remember one time, such an expert illustrated his point with some "established" data on down. He left enough information in the illustration from which one did track down the original source. The data was actually data on chicken feather/down mixtures, and was over 50 years old. He retracted the old data and substituted new data. I found that the original source for the new data was a paper published from Natick Laboratories (US Army) [the "new data" was unsourced].
I am no "expert" at down, and urge great caution in selecting sources of "qualified experts".