Transmission mount with engine and mid plate.
A solid trans mount is asking for trouble. I have a very stiff tube chassis, yet use shock biscuits, four of them, to allow give for chassis flex. Build it to put some upward pressure on the trans, (about enough to support its weight) and let those shock biscuits limit the loads the case has to put up with due to chassis flex. And i don't care how good a person thinks their chassis is, Everything bends some!