Regner Paul tram loco with heat shield and secondary air hole

After fitting the heat shield I still wasn't happy with the way my Regner tram's burner was sounding. I dismantled the loco (breaking the steam pipe where it went into the super heater in the process), re-assembled everything and then discovered that all the other Regner trams had a secondary air hole in the burner's collar. I milled out a similar air hole in my tram's burner and this made the burner both quieter and the flame more regular. Other than that I didn't find any difference, so I still think the heat shield I'd made is necessary, especially when I heard from other tram owners that 4 of them had had to replace the cylinder springs which been heat damaged.