@heinduplessis, Add a bit more of expo? I didn't saw any pics of the underside, have you also re-enforced it?
The extra weight+speed will make it flex more making it more unstable.
That convinced me to to finally convert mine to FPV.
Going to get a mount like this :
Wing Motor Mount
And swap the motor to one more powerful, need to put some CF in it as well to give more strength.
PS: My Swift2 has now +6yrs and it's still flying.