Grand Canyon flying minimum altitudes
The rules for operations in the Grand Canyon Special Flight Rules Area (SFRA) are governed under 14 CFR Part 93, Subpart U.

Please review these rules here and all applicable GCSFRA NOTAMS prior to departure.  Also perform your performance calculations for the predicted density altitude on the day of your flight to verify your aircraft will be capable of ascending to at least 9500 ft MSL, else it may not be legally or physically possible to make the flight.

For an eastbound flight like that departing 1G4, I’d recommend a takeoff and climb to 9500 ft MSL (eastbound VFR altitude which meets the minimum requirements of both the Pearce Ferry and Diamond Creek sectors of the GCSFRA) prior to overflying the Pearce Ferry sector enroute for 1Z1.  Be advised for both fixed wing and rotor wing aircraft over the northern sections of the Pearce Ferry and Diamond Creek sectors.  Commence your descent into 1Z1 only once clear of the northern edge of the Diamond Creek sector.

Aside from the legal aspects, keep in mind that you are going to be flying over some pretty rugged country out there.  Have a plan of action should an engine failure or other inflight emergency occur enroute, requiring you to set the aircraft down somewhere.