A mid plate is more than an engine mount, if it is properly mounted it stiffens the firewall area of the chassis and adds as a safety net of sorts if there is a catastrophic transmission failure. Not knowing what chassis aids you have ( full cage, roll bar only?? ) a properly sized mid plate can be mounted at the bottom and top to chassis/frame members and significantly reduce twist between the engine mount and forward rear suspension mount . Again more needs to be known about the car to give more in-depth opinion. but my vote if it’s a race car with modified chassis/body components it should at least have a 1/8" mid plate as a trans failure safety mechanism.