That's now on my list for one of the next updates ;)
Sorry to create more work for you, but I suspect you are a bit of a perfectionist so would like to make things as best as possible. Since there are no deadlines to your work, you can prioritize and do only what is most important and leave the rest for later.
I know absolutely nothing about programming, so I have no idea how all that "magic" happens with beneficiaries, but I suspected it would not be easy to wait until pay-out to grab the percentage. It was just an idea and might not be feasible. However, where there is a will, there is a way. It might be more complex, but I suspect you could mine the data of past earnings and create some average. Those who get over a certain average weekly or monthly earning would be affected while the remainder are not. By using past earnings, you also ensure that someone who has JUST broken into the threshold is not immediately penalized. That way if it was a one-time deal where a nice trail passed through, they don't automatically lose some of their earnings. Only when they make consistent good earnings will they need to pay the user fee.