I ran German spongies on a couple of my entries for the proxy races and they seem to have hooked up fine.
They were originally made by the German company Graupner, hence the name.
They still work because they come with a skin over the sponge, and once you take the skin off, the sponge material is generally still fresh. They were not only used on dragsters: they were also the tire of choice from fairly early in the game (63 or before) on road cars in both scales, until the closed-cell foam/sponge tires came along. Mike Morissey still used German spongies on the car in his first how-to scratchbuilt article in Car Model, April 66 issue.
Once or twice, on old cars I've bought on ebay, the same principle has applied: there was so much goop left on the closed-cell tire that once I cleaned it off, it was still pretty fresh!
When we first started vintage racing here some 25 years ago, before silicones or urethanes were widely available, we tended to use the old German sponge tires like Mila Miglia or Rannalli on our slick polyurethane painted club track, and they worked ok if we cleaned them with lighter fluid every 10 laps or so...
The original Graupners had very small holes to fit on model airplane wheels, so these had to be opened up before using on slot car wheels. The early slot manufacturers, did this for you, and eventually offered them mounted and sometimes glued and trimmed.
Don
Tire evolution: