The festoon bulbs arrived today and I put them in. The 41 mm are ok, but the 39 mm would work just as well. They're fine, the only thing is that despite being called "super white" they do have a distinct bluish tinge to the light. That's fine for the trunk, and in a modern car the bluish tinge might seem cool, but in my palomino-interior car I think the more yellowish light of the incandescent bulbs might "go better".
Anyway: they provide bluish-white light, somewhat brighter than the light bulb, with no heat and presumably negligible current draw. 100% recommended for the trunk. Whether the increase in brightness (I'll shoot from the hip and say 1/3 more light) is worth the bluish color is subjective.