If do fully guided surgery can have milled prior to surgery Orentlicher 2013
Leave a bit of the palate though to aid in seating. Seen in this video at 10:30 Digital Treatment Protocols: Implant Therapy By Siamak Abai
Basically same as making a denture level the opposing.
But use PREAT emesh for strength or metal
eFiber Hybrid frame
Fiber Force is another one
Fiber Force CST looking to be cheap easy substructure