To amplify what James wrote, the "party line" has to be that you can't put a Pioneer or Stages type meter on a Serios with the standard brake, because that's true most
of the time.
It turns out that some crank arm lengths actually do
fit because the arms have a slightly different shape. Millimeter differences add up quickly.
So, if you happen to hear from someone that they were able to get a Stages meter on a stock Serios, they probably weren't lying to you. It's just complicated.
As mentioned in a previous thread, I'm working to put together a database of known good combinations for the Diamondback bikes, but it's... a lot of work.
Custom Studio Manager for Diamondback Bikes.
Coaching and bike fit - http://source-e.net/
Cyclocross blog - https://crosssports.net/