I have tracked the values for the MaxStep size down into TG4GeometryManager.cxx
Here the G4UserLimit is created:
G4UserLimits* limits = 0;
if ( stemax > 0 ) {
limits = new G4UserLimits();
limits->SetMaxAllowedStep(stemax*cm);
G4cout<<"MaxAllowedStep="<<stemax*cm<<G4endl;
}
If I put a value of 0.5 in the file, the value of stemax*cm is 5 !!
Sebastian.