Folks, I have an update!
Although when I was using the 100 watt Hella lamps there was no heat damage to the housings, I've discovered there was. But not to the plastic.
In front of the bulb is that clipped in metal shroud with slots in it. The arms that clip into the rear of the housing are a spring metal. It's these arms that were affected by the heat. The arms wandered closer together and the shroud dropped into the housing.
As the HIR 9011 lamps I switched to are high beam bulbs, they don't have a shrouded tip and the metal shroud of the housing keeps it a low beam housing. To continue using these bulbs, I had to open the housing to get the thing back in place. I bent the arms out so it'd stay in place again.
While I was at it I foiled over the slots in the shroud.
Cutting the housing open was a pain, about a half hour with the Dremel tool. I drilled two tiny holes on opposite sides for some safety wire to hold it together then sealed it with Ultra Blue silicone.