We have been running trial dogs for over 26 years, yikes that is over a quarter century. The first three titled out as one sided, the last four titled out as two sided and I would not go back to a one sided dog. My wife does not train as much as I do but she handles them proficiently on either side even though her time training them is more restricted. Chris Atkinson has neatly laid out the who, when and how to two side a dog. The key is to start early and be consistent.