The main problem with multi BLD is that it's hard to fit all the scrambles on a page, and a scrambles set is not as nice if it spans multiple pages. The number of scrambles can be set to anything, but the number of scrambles that print on a single page depend on the browser and the page zoom level.
It's easy to change the amount, so I've been assuming that the organizer will remember to increase the bound if someone like Zane is coming. There have been very few attempts over 20 cubes. However, I've decreased the drawing size to fit 28 (the new default) on a page. This means that organizers should be able to select rounds without worrying about the number of scrambles, at least for a while.