Yep, maybe make it not as wide with no holes, if that's stronger.
Not sure about how much load the front diff mount takes. I do know if the mount is worn out the diff wants to tilt up into the underside of the car, which is why there's an strap over the top of it. I'm no engineer but, I'd think most of the loads are on the mustache bar. I think the front mount is just there to stop the upwards motion.
Stevo: Some torque figures I found on Hybrid Z
Modified L24:
231.5 HP at the wheels
195.9 lbft torque
Turbo L28:
341.44whp
390.31 lbft torque
at 23.7lbs max boost
Another turbo L28:
403.16 whp
365.92 lbft torque
at 17lbs max boost
Not sure where that torque is though.. engine, or wheels?