I would say 6s would be fine, they are rated for 6s and many run 6s on the 16018 as well as the 22418 without issues. I did get the 16024 for a little voltage headroom with motor brakes in a heavy Muggy on 6s and if I decided I needed 8s at a later date. My charger and BEC are rated to 8s also, so I figured it was a good option to have.