[tsungxu]

I used single wall foaming PLA which has filament density of ~0.45 g/cm3 at 250 degree nozzle temp, about 64% lower than normal PLA. But it is even worse for impact resistance than normal PLA. Weight was the primary driver for this plane

[stavros]

Yep, I've used that as well, but, as you say, it's just very bad for impact resistance. I think the sweet spot between weight and durability might be ABS or something like ASA.

[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.