XF-11 prop reverse bindings

I just bought the XF-11 and it’s excellent. Also, I like to support the developer given the excellent and free Scrapy.
Anyway, anyone out there been able to figure out how to bind controllers to prop reversers? I have a Honeycomb Bravo and have no problems with all other planes but with this one I can’t seem to get the prop reversers to function.
Thanks for your help.