From all the research I've done thus far and the RKIs I have chatted with, 500 to 1,000 gallon/acre yields seem realistic, IF they could be harvested on a large scale. The challenge is harvesting the berries economicially, that's why no one has already done this. And it is a huge, seemingly insurmountable challenge. At this point I have serious doubts it could be feasible due to all the little problems. In China where manual labor is dirt cheap, they harvest by hand, but because of other factors their culitivation of Tallow tree berries is on the decline.
The current line of thinking is to get one of those tree shakers like they use to harvest pecans with. We're likely going to give it a shot, but this year's berries wouldn't be ripe enough until fall.
And because it is considered a noxious weed by many (and it really is), it would be a really bad idea to introduce them somewhere where they haven't already invaded.