I modify the handling to change it to suit my tastes.. My car rides harder because of stiffer springs and larger wheels.. handles better than oem that was a trade off, one that I don't mind. M previous car was a boring Ford Escape that I had no interest in modifying because it was just a boring car. I intend to keep this as my paid off high mileage car so I'm gonna modify it to suit my tastes, but I still want it to last a long time too, this is why I am interested in the reinforcement. As far as oversteer is concerned, in my setup and driving style, oversteer would not be a issue, it would probably get my handling more where I want it. I seem to encounter understeer more often. As for reinforcement bar they are not used to "improve handling" per say, but to reduce body flex. I would expect a change in handling from a sway bar, I wouldn't from a lower arm bar. Those bars aren't standard equipment on any OEM vehicles usually, and the ones that do have those types of things oem are performance models. There is nothing "knee-jerk" about it, I've had the car over a year, already have a lot of miles on it, drive it hard and certain reinforcement bars may not be a bad investment for me. Also, Corksport isn't unknown nor is it the only company offering such things (although not much for the CX-5). Autoexe has more to offer, but JDM shipping. I looked into Ultra Racing, they actually seem pretty legitimate, but I'm not ready to buy from them yet. In general those bars aren't sophisticated, as long as they are properly mounted so that loads are transferred from one side to the other, they serve a purpose.
