[tsungxu]

Yes and there is foaming ASA as well which is almost as light as foaming PLA. But I can't print ASA well on my A1 and the weight penalty was still enough that I didn't try, given the mission profile of flight time.

[sandos]

Did I dream or is there even foaming TPU? TPU in general seems almost indestructible to me so should be good :)

[regularfry]

Colorfabb Varioshore, among others. It's extremely neat stuff.