Provide a chunksize for map?

First of all, let me say great job on tackling this issue. I tried using both concurrent futures and pebble, and both lock up during very long tasks. I'm trying to test futureproof with my use case, but it's going really slow and timing out my Python RQ workers. The same thing was happening on concurrent futures and pebble till I provided a chunksize argument to the map function, is there a way I can do this with futureproof?