There are some actually really cool balsa 3D electrics that the 15L would do fine in. The 4:1 gearbox is just a little high for 3D props IMHO, but they can't make a planetary any lower that physical size. Still, with good packs it'll swing an 11X4.7, so the little balsa planes (or even bigger 44" foamies) would still be cool. I'm gonna slap an 18L in a C box and try some 13~14" props [8D]