Change Bit Rate of DNxHD with Alpha

Is there any way to export DNxHD or DNxHR with an alpha channel and a bit rate lower than 574Mbps? So far every codec I've tried exports with the same bit rate of 574Mbps, here's what I've tried:

DNxHD SQ

DNxHD HQ

DNxHR HQ

When I export using Cineform it exports at 272Mbps so I get a much more manageable file size, unfortunately the client I'm working with only accepts DNxHD so I'm trying to make it work.

What's weird is, according to this codec comparison page there is no Avid codec with a bit rate of 574Mbps so I don't know where that's coming from: https://blog.frame.io/2017/02/13/50-intermediate-codecs-compared/

Any and all help is appreciated.

Thanks!